diff --git a/_unittests/ut_onnxrt/test_onnxrt_python_runtime_ml.py b/_unittests/ut_onnxrt/test_onnxrt_python_runtime_ml.py
index 3fda34185..ee8ddfe7b 100644
--- a/_unittests/ut_onnxrt/test_onnxrt_python_runtime_ml.py
+++ b/_unittests/ut_onnxrt/test_onnxrt_python_runtime_ml.py
@@ -282,8 +282,11 @@ def test_dict_vectorizer(self):
         data = [{"amy": 1.0, "chin": 200.0}, {"nice": 3.0, "amy": 1.0}]
         model.fit_transform(data)
         exp = model.transform(data)
-        model_def = convert_sklearn(model, "dictionary vectorizer",
-                                    [("input", DictionaryType(StringTensorType([1]), FloatTensorType([1])))])
+        model_def = convert_sklearn(
+            model, "dictionary vectorizer",
+            [("input", DictionaryType(
+                StringTensorType([1]),
+                FloatTensorType([1])))])
         oinf = OnnxInference(model_def)
         array_data = numpy.array(data)
         got = oinf.run({'input': array_data})
diff --git a/_unittests/ut_onnxrt/test_onnxrt_python_runtime_ml_text.py b/_unittests/ut_onnxrt/test_onnxrt_python_runtime_ml_text.py
index d999a62d9..55abe52da 100644
--- a/_unittests/ut_onnxrt/test_onnxrt_python_runtime_ml_text.py
+++ b/_unittests/ut_onnxrt/test_onnxrt_python_runtime_ml_text.py
@@ -18,7 +18,8 @@
 from skl2onnx.common.data_types import (
     StringTensorType, FloatTensorType, Int64TensorType)
 from skl2onnx.algebra.onnx_ops import (  # pylint: disable=E0611
-    OnnxStringNormalizer, OnnxTfIdfVectorizer, OnnxLabelEncoder)
+    OnnxStringNormalizer, OnnxTfIdfVectorizer, OnnxLabelEncoder,
+    OnnxCategoryMapper)
 from mlprodict.onnx_conv import to_onnx
 from mlprodict.onnx_conv.onnx_ops import OnnxTokenizer
 from mlprodict.onnxrt import OnnxInference
@@ -473,6 +474,35 @@ def test_multi_output_classifier(self):
         for e, g in zip(expected_proba, got['probabilities']):
             self.assertEqualArray(e, g, decimal=5)
 
+    def test_onnxrt_category_mapper_intstr(self):
+
+        op = OnnxCategoryMapper(
+            'cat', op_version=TARGET_OPSET,
+            cats_int64s=[1, 2], cats_strings=["cat1", "cat2"],
+            output_names=['out'])
+        onx = op.to_onnx(
+            inputs=[('cat', Int64TensorType())],
+            outputs=[('out', StringTensorType())])
+        oinf = OnnxInference(onx)
+        res = oinf.run({'cat': numpy.array([1, 2, 1, 5], dtype=numpy.int64)})
+        self.assertEqual(
+            res['out'].tolist(), ["cat1", "cat2", "cat1", ""])
+
+    def test_onnxrt_category_mapper_strint(self):
+
+        op = OnnxCategoryMapper(
+            'cat', op_version=TARGET_OPSET,
+            cats_int64s=[1, 2], cats_strings=["cat1", "cat2"],
+            output_names=['out'])
+        onx = op.to_onnx(
+            inputs=[('cat', StringTensorType())],
+            outputs=[('out', Int64TensorType())])
+        oinf = OnnxInference(onx)
+        res = oinf.run({'cat': numpy.array(["cat1", "cat2", "cat1", "R"],
+                                           dtype=numpy.str_)})
+        self.assertEqualArray(
+            res['out'], numpy.array([1, 2, 1, -1], dtype=numpy.int64))
+
 
 if __name__ == "__main__":
-    unittest.main()
+    unittest.main(verbosity=2)
diff --git a/mlprodict/onnxrt/ops_cpu/_op_list.py b/mlprodict/onnxrt/ops_cpu/_op_list.py
index f2b4d19f2..f8ce868fd 100644
--- a/mlprodict/onnxrt/ops_cpu/_op_list.py
+++ b/mlprodict/onnxrt/ops_cpu/_op_list.py
@@ -27,6 +27,7 @@
 from .op_ceil import Ceil
 from .op_celu import Celu
 from .op_clip import Clip_6, Clip_11, Clip
+from .op_category_mapper import CategoryMapper
 from .op_complex_abs import ComplexAbs
 from .op_compress import Compress
 from .op_concat import Concat
diff --git a/mlprodict/onnxrt/ops_cpu/op_category_mapper.py b/mlprodict/onnxrt/ops_cpu/op_category_mapper.py
new file mode 100644
index 000000000..cece6ad49
--- /dev/null
+++ b/mlprodict/onnxrt/ops_cpu/op_category_mapper.py
@@ -0,0 +1,60 @@
+# -*- encoding: utf-8 -*-
+# pylint: disable=E0203,E1101,C0111
+"""
+@file
+@brief Runtime operator.
+"""
+import numpy
+from ._op import OpRun
+
+
+class CategoryMapper(OpRun):
+
+    atts = {'cats_int64s': numpy.empty(0, dtype=numpy.int64),
+            'cats_strings': numpy.empty(0, dtype=numpy.str_),
+            'default_int64': -1,
+            'default_string': b'',
+            }
+
+    def __init__(self, onnx_node, desc=None, **options):
+        OpRun.__init__(self, onnx_node, desc=desc,
+                       expected_attributes=CategoryMapper.atts,
+                       **options)
+        if len(self.cats_int64s) != len(self.cats_strings):
+            raise RuntimeError(
+                "Lengths mismatch between cats_int64s (%d) and "
+                "cats_strings (%d)." % (
+                    len(self.cats_int64s), len(self.cats_strings)))
+        self.int2str_ = {}
+        self.str2int_ = {}
+        for a, b in zip(self.cats_int64s, self.cats_strings):
+            be = b.decode('utf-8')
+            self.int2str_[a] = be
+            self.str2int_[be] = a
+
+    def _run(self, x):  # pylint: disable=W0221
+        if x.dtype == numpy.int64:
+            xf = x.ravel()
+            res = [self.int2str_.get(xf[i], self.default_string)
+                   for i in range(0, xf.shape[0])]
+            return (numpy.array(res).reshape(x.shape), )
+
+        xf = x.ravel()
+        res = numpy.empty((xf.shape[0], ), dtype=numpy.int64)
+        for i in range(0, res.shape[0]):
+            res[i] = self.str2int_.get(xf[i], self.default_int64)
+        return (res.reshape(x.shape), )
+
+    def _infer_shapes(self, x):  # pylint: disable=W0221
+        if x.dtype == numpy.int64:
+            return (x.copy(dtype=numpy.str_), )
+        return (x.copy(dtype=numpy.int64), )
+
+    def _infer_types(self, x):  # pylint: disable=W0221
+        if x.dtype == numpy.int64:
+            return (numpy.str_, )
+        return (numpy.int64, )
+
+    def _infer_sizes(self, *args, **kwargs):
+        res = self.run(*args, **kwargs)
+        return (dict(temp=0), ) + res