diff --git a/.circleci/config.yml b/.circleci/config.yml
index dfb28bd6fd..e7a56ffd24 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -70,7 +70,7 @@ jobs:
             . venv/bin/activate
             mkdir test-reports
             pip freeze > test-reports/pip_versions.txt
-            pytest -n 2 --cov=ml-agents --cov=ml-agents-envs --cov=gym-unity --cov-report html --junitxml=test-reports/junit.xml -p no:warnings
+            pytest --cov=ml-agents --cov=ml-agents-envs --cov=gym-unity --cov-report html --junitxml=test-reports/junit.xml -p no:warnings
 
       - run:
           name: Verify there are no hidden/missing metafiles.
diff --git a/experiment_torch.py b/experiment_torch.py
index 4fcdf8a2de..6fe65c15d7 100644
--- a/experiment_torch.py
+++ b/experiment_torch.py
@@ -98,8 +98,8 @@ def run_experiment(
         evaluate_count = evaluate["TorchPolicy.evaluate"]["count"]
     else:
         if algo == "ppo":
-            update_total = update["TFPPOOptimizer.update"]["total"]
-            update_count = update["TFPPOOptimizer.update"]["count"]
+            update_total = update["PPOOptimizer.update"]["total"]
+            update_count = update["PPOOptimizer.update"]["count"]
         else:
             update_total = update["SACTrainer._update_policy"]["total"]
             update_count = update["SACTrainer._update_policy"]["count"]
diff --git a/ml-agents/mlagents/trainers/cli_utils.py b/ml-agents/mlagents/trainers/cli_utils.py
index 41f2c3d87a..8f82751d3f 100644
--- a/ml-agents/mlagents/trainers/cli_utils.py
+++ b/ml-agents/mlagents/trainers/cli_utils.py
@@ -168,6 +168,13 @@ def _create_parser() -> argparse.ArgumentParser:
         action=DetectDefaultStoreTrue,
         help="Forces training using CPU only",
     )
+    argparser.add_argument(
+        "--torch",
+        default=False,
+        action=DetectDefaultStoreTrue,
+        help="(Experimental) Use the PyTorch framework instead of TensorFlow. Install PyTorch "
+        "before using this option",
+    )
 
     eng_conf = argparser.add_argument_group(title="Engine Configuration")
     eng_conf.add_argument(
diff --git a/ml-agents/mlagents/trainers/ppo/optimizer_tf.py b/ml-agents/mlagents/trainers/ppo/optimizer_tf.py
index 51116f2302..323ca640fe 100644
--- a/ml-agents/mlagents/trainers/ppo/optimizer_tf.py
+++ b/ml-agents/mlagents/trainers/ppo/optimizer_tf.py
@@ -9,7 +9,7 @@
 from mlagents.trainers.settings import TrainerSettings, PPOSettings
 
 
-class TFPPOOptimizer(TFOptimizer):
+class PPOOptimizer(TFOptimizer):
     def __init__(self, policy: TFPolicy, trainer_params: TrainerSettings):
         """
         Takes a Policy and a Dict of trainer parameters and creates an Optimizer around the policy.
diff --git a/ml-agents/mlagents/trainers/ppo/trainer.py b/ml-agents/mlagents/trainers/ppo/trainer.py
index a06396a617..b0ffae03c8 100644
--- a/ml-agents/mlagents/trainers/ppo/trainer.py
+++ b/ml-agents/mlagents/trainers/ppo/trainer.py
@@ -10,19 +10,25 @@
 from mlagents_envs.logging_util import get_logger
 from mlagents_envs.base_env import BehaviorSpec
 from mlagents.trainers.trainer.rl_trainer import RLTrainer
-from mlagents.trainers.policy.torch_policy import TorchPolicy
 from mlagents.trainers.policy import Policy
 from mlagents.trainers.policy.tf_policy import TFPolicy
-from mlagents.trainers.ppo.optimizer_torch import TorchPPOOptimizer
-from mlagents.trainers.ppo.optimizer_tf import TFPPOOptimizer
+from mlagents.trainers.ppo.optimizer_tf import PPOOptimizer
 from mlagents.trainers.trajectory import Trajectory
 from mlagents.trainers.behavior_id_utils import BehaviorIdentifiers
 from mlagents.trainers.settings import (
     TrainerSettings,
     PPOSettings,
     TestingConfiguration,
+    FrameworkType,
 )
 
+try:
+    from mlagents.trainers.policy.torch_policy import TorchPolicy
+    from mlagents.trainers.ppo.optimizer_torch import TorchPPOOptimizer
+except ModuleNotFoundError:
+    TorchPolicy = None  # type: ignore
+    TorchPPOOptimizer = None  # type: ignore
+
 
 logger = get_logger(__name__)
 
@@ -58,7 +64,6 @@ def __init__(
         )
         self.load = load
         self.seed = seed
-        self.framework = "torch" if TestingConfiguration.use_torch else "tf"
         if TestingConfiguration.max_steps > 0:
             self.trainer_settings.max_steps = TestingConfiguration.max_steps
         self.policy: Policy = None  # type: ignore
@@ -254,12 +259,12 @@ def add_policy(
             )
         self.policy = policy
         self.policies[parsed_behavior_id.behavior_id] = policy
-        if self.framework == "torch":
+        if self.framework == FrameworkType.PYTORCH:
             self.optimizer = TorchPPOOptimizer(  # type: ignore
                 self.policy, self.trainer_settings  # type: ignore
             )  # type: ignore
         else:
-            self.optimizer = TFPPOOptimizer(  # type: ignore
+            self.optimizer = PPOOptimizer(  # type: ignore
                 self.policy, self.trainer_settings  # type: ignore
             )  # type: ignore
         for _reward_signal in self.optimizer.reward_signals.keys():
diff --git a/ml-agents/mlagents/trainers/sac/trainer.py b/ml-agents/mlagents/trainers/sac/trainer.py
index fea60e143d..13dd46ecc0 100644
--- a/ml-agents/mlagents/trainers/sac/trainer.py
+++ b/ml-agents/mlagents/trainers/sac/trainer.py
@@ -18,10 +18,14 @@
 from mlagents.trainers.trainer.rl_trainer import RLTrainer
 from mlagents.trainers.trajectory import Trajectory, SplitObservations
 from mlagents.trainers.behavior_id_utils import BehaviorIdentifiers
-from mlagents.trainers.policy.torch_policy import TorchPolicy
-from mlagents.trainers.sac.optimizer_torch import TorchSACOptimizer
-from mlagents.trainers.settings import TrainerSettings, SACSettings
+from mlagents.trainers.settings import TrainerSettings, SACSettings, FrameworkType
 
+try:
+    from mlagents.trainers.policy.torch_policy import TorchPolicy
+    from mlagents.trainers.sac.optimizer_torch import TorchSACOptimizer
+except ModuleNotFoundError:
+    TorchPolicy = None  # type: ignore
+    TorchSACOptimizer = None  # type: ignore
 
 logger = get_logger(__name__)
 
@@ -353,7 +357,7 @@ def add_policy(
             )
         self.policy = policy
         self.policies[parsed_behavior_id.behavior_id] = policy
-        if self.framework == "torch":
+        if self.framework == FrameworkType.PYTORCH:
             self.optimizer = TorchSACOptimizer(  # type: ignore
                 self.policy, self.trainer_settings  # type: ignore
             )  # type: ignore
diff --git a/ml-agents/mlagents/trainers/settings.py b/ml-agents/mlagents/trainers/settings.py
index fc6f341970..bb170349ec 100644
--- a/ml-agents/mlagents/trainers/settings.py
+++ b/ml-agents/mlagents/trainers/settings.py
@@ -524,6 +524,11 @@ def to_settings(self) -> type:
         return _mapping[self]
 
 
+class FrameworkType(Enum):
+    TENSORFLOW: str = "tensorflow"
+    PYTORCH: str = "pytorch"
+
+
 @attr.s(auto_attribs=True)
 class TrainerSettings(ExportableSettings):
     trainer_type: TrainerType = TrainerType.PPO
@@ -546,6 +551,7 @@ def _set_default_hyperparameters(self):
     threaded: bool = True
     self_play: Optional[SelfPlaySettings] = None
     behavioral_cloning: Optional[BehavioralCloningSettings] = None
+    framework: FrameworkType = FrameworkType.TENSORFLOW
 
     cattr.register_structure_hook(
         Dict[RewardSignalType, RewardSignalSettings], RewardSignalSettings.structure
@@ -713,7 +719,13 @@ def from_argparse(args: argparse.Namespace) -> "RunOptions":
                     configured_dict["engine_settings"][key] = val
                 else:  # Base options
                     configured_dict[key] = val
-        return RunOptions.from_dict(configured_dict)
+
+        # Apply --torch retroactively
+        final_runoptions = RunOptions.from_dict(configured_dict)
+        if "torch" in DetectDefault.non_default_args:
+            for trainer_set in final_runoptions.behaviors.values():
+                trainer_set.framework = FrameworkType.PYTORCH
+        return final_runoptions
 
     @staticmethod
     def from_dict(options_dict: Dict[str, Any]) -> "RunOptions":
diff --git a/ml-agents/mlagents/trainers/tests/test_ppo.py b/ml-agents/mlagents/trainers/tests/test_ppo.py
index 5ea9f11bd5..11496ad3bd 100644
--- a/ml-agents/mlagents/trainers/tests/test_ppo.py
+++ b/ml-agents/mlagents/trainers/tests/test_ppo.py
@@ -8,7 +8,7 @@
 from mlagents.trainers.behavior_id_utils import BehaviorIdentifiers
 
 from mlagents.trainers.ppo.trainer import PPOTrainer, discount_rewards
-from mlagents.trainers.ppo.optimizer_tf import TFPPOOptimizer
+from mlagents.trainers.ppo.optimizer_tf import PPOOptimizer
 from mlagents.trainers.policy.tf_policy import TFPolicy
 from mlagents.trainers.agent_processor import AgentManagerQueue
 from mlagents.trainers.tests import mock_brain as mb
@@ -52,7 +52,7 @@ def _create_ppo_optimizer_ops_mock(dummy_config, use_rnn, use_discrete, use_visu
     policy = TFPolicy(
         0, mock_specs, trainer_settings, "test", False, create_tf_graph=False
     )
-    optimizer = TFPPOOptimizer(policy, trainer_settings)
+    optimizer = PPOOptimizer(policy, trainer_settings)
     return optimizer
 
 
diff --git a/ml-agents/mlagents/trainers/tests/test_reward_signals.py b/ml-agents/mlagents/trainers/tests/test_reward_signals.py
index 5ccbfe8836..44daf6713e 100644
--- a/ml-agents/mlagents/trainers/tests/test_reward_signals.py
+++ b/ml-agents/mlagents/trainers/tests/test_reward_signals.py
@@ -4,7 +4,7 @@
 import mlagents.trainers.tests.mock_brain as mb
 from mlagents.trainers.policy.tf_policy import TFPolicy
 from mlagents.trainers.sac.optimizer import SACOptimizer
-from mlagents.trainers.ppo.optimizer_tf import TFPPOOptimizer
+from mlagents.trainers.ppo.optimizer_tf import PPOOptimizer
 from mlagents.trainers.tests.test_simple_rl import PPO_CONFIG, SAC_CONFIG
 from mlagents.trainers.settings import (
     GAILSettings,
@@ -75,7 +75,7 @@ def create_optimizer_mock(
     if trainer_settings.trainer_type == TrainerType.SAC:
         optimizer = SACOptimizer(policy, trainer_settings)
     else:
-        optimizer = TFPPOOptimizer(policy, trainer_settings)
+        optimizer = PPOOptimizer(policy, trainer_settings)
     return optimizer
 
 
diff --git a/ml-agents/mlagents/trainers/tests/test_rl_trainer.py b/ml-agents/mlagents/trainers/tests/test_rl_trainer.py
index 9736df2fd8..6aac069310 100644
--- a/ml-agents/mlagents/trainers/tests/test_rl_trainer.py
+++ b/ml-agents/mlagents/trainers/tests/test_rl_trainer.py
@@ -25,7 +25,10 @@ def _update_policy(self):
     def add_policy(self, mock_behavior_id, mock_policy):
         self.policies[mock_behavior_id] = mock_policy
 
-    def create_policy(self):
+    def create_tf_policy(self):
+        return mock.Mock()
+
+    def create_torch_policy(self):
         return mock.Mock()
 
     def _process_trajectory(self, trajectory):
diff --git a/ml-agents/mlagents/trainers/tests/torch/test_networks.py b/ml-agents/mlagents/trainers/tests/torch/test_networks.py
index b6b93698f1..ff5209b676 100644
--- a/ml-agents/mlagents/trainers/tests/torch/test_networks.py
+++ b/ml-agents/mlagents/trainers/tests/torch/test_networks.py
@@ -40,6 +40,7 @@ def test_networkbody_vector():
 
 
 def test_networkbody_lstm():
+    torch.manual_seed(0)
     obs_size = 4
     seq_len = 16
     network_settings = NetworkSettings(
@@ -64,6 +65,7 @@ def test_networkbody_lstm():
 
 
 def test_networkbody_visual():
+    torch.manual_seed(0)
     vec_obs_size = 4
     obs_size = (84, 84, 3)
     network_settings = NetworkSettings()
@@ -89,6 +91,7 @@ def test_networkbody_visual():
 
 
 def test_valuenetwork():
+    torch.manual_seed(0)
     obs_size = 4
     num_outputs = 2
     network_settings = NetworkSettings()
diff --git a/ml-agents/mlagents/trainers/trainer/rl_trainer.py b/ml-agents/mlagents/trainers/trainer/rl_trainer.py
index fdd90e11b3..9768a03ebf 100644
--- a/ml-agents/mlagents/trainers/trainer/rl_trainer.py
+++ b/ml-agents/mlagents/trainers/trainer/rl_trainer.py
@@ -19,13 +19,18 @@
 from mlagents_envs.timers import hierarchical_timer
 from mlagents_envs.base_env import BehaviorSpec
 from mlagents.trainers.policy.policy import Policy
-from mlagents.trainers.policy.torch_policy import TorchPolicy
 from mlagents.trainers.policy.tf_policy import TFPolicy
 from mlagents.trainers.behavior_id_utils import BehaviorIdentifiers
 from mlagents.trainers.agent_processor import AgentManagerQueue
 from mlagents.trainers.trajectory import Trajectory
-from mlagents.trainers.settings import TestingConfiguration
+from mlagents.trainers.settings import TestingConfiguration, FrameworkType
 from mlagents.trainers.stats import StatsPropertyType
+from mlagents.trainers.exception import UnityTrainerException
+
+try:
+    from mlagents.trainers.policy.torch_policy import TorchPolicy
+except ModuleNotFoundError:
+    TorchPolicy = None  # type: ignore
 
 RewardSignalResults = Dict[str, RewardSignalResult]
 
@@ -50,7 +55,8 @@ def __init__(self, *args, **kwargs):
         self._stats_reporter.add_property(
             StatsPropertyType.HYPERPARAMETERS, self.trainer_settings.as_dict()
         )
-        self.framework = "torch" if TestingConfiguration.use_torch else "tf"
+        self.framework = self.trainer_settings.framework
+        logger.debug(f"Using framework {self.framework.value}")
         if TestingConfiguration.max_steps > 0:
             self.trainer_settings.max_steps = TestingConfiguration.max_steps
         self._next_save_step = 0
@@ -99,7 +105,11 @@ def _is_ready_update(self):
     def create_policy(
         self, parsed_behavior_id: BehaviorIdentifiers, behavior_spec: BehaviorSpec
     ) -> Policy:
-        if self.framework == "torch":
+        if self.framework == FrameworkType.PYTORCH and TorchPolicy is None:
+            raise UnityTrainerException(
+                "To use the experimental PyTorch backend, install the PyTorch Python package first."
+            )
+        elif self.framework == FrameworkType.PYTORCH:
             return self.create_torch_policy(parsed_behavior_id, behavior_spec)
         else:
             return self.create_tf_policy(parsed_behavior_id, behavior_spec)
@@ -165,6 +175,9 @@ def save_model(self) -> None:
             logger.warning(
                 "Trainer has multiple policies, but default behavior only saves the first."
             )
+        elif n_policies == 0:
+            logger.warning("Trainer has no policies, not saving anything.")
+            return
         policy = list(self.policies.values())[0]
         settings = SerializationSettings(policy.model_path, self.brain_name)
         model_checkpoint = self._checkpoint()
diff --git a/test_requirements.txt b/test_requirements.txt
index 08193c7ac9..967c4f635e 100644
--- a/test_requirements.txt
+++ b/test_requirements.txt
@@ -3,5 +3,8 @@ pytest>4.0.0,<6.0.0
 pytest-cov==2.6.1
 pytest-xdist
 
+# PyTorch tests are here for the time being, before they are used in the codebase.
+torch>=1.5.0
+
 # onnx doesn't currently have a wheel for 3.8
 tf2onnx>=1.5.5;python_version<'3.8'