diff --git a/src/model/preprocessing.rs b/src/model/preprocessing.rs
index 822f29d..c7dc0ee 100644
--- a/src/model/preprocessing.rs
+++ b/src/model/preprocessing.rs
@@ -1,12 +1,14 @@
 //! Utilities for data preprocessing.
 
-use crate::settings::PreProcessing;
+use crate::model::error::ModelError;
+use crate::settings::{PreProcessing, SettingsError};
 use crate::utils::features::{FeatureError, interaction_features, polynomial_features};
 use smartcore::{
     decomposition::{
         pca::{PCA, PCAParameters},
         svd::{SVD, SVDParameters},
     },
+    error::Failed,
     linalg::{
         basic::arrays::{Array, Array2},
         traits::{
@@ -52,72 +54,103 @@ where
         }
     }
 
-    /// Train preprocessing models based on settings.
-    pub fn train(&mut self, x: &InputArray, settings: &PreProcessing) {
+    /// Fit preprocessing state (if required) and return a transformed copy of the
+    /// training matrix.
+    pub fn fit_transform(
+        &mut self,
+        x: InputArray,
+        settings: &PreProcessing,
+    ) -> Result<InputArray, SettingsError> {
+        self.pca = None;
+        self.svd = None;
         match settings {
+            PreProcessing::None => Ok(x),
+            PreProcessing::AddInteractions => {
+                interaction_features(x).map_err(Self::feature_error_to_settings)
+            }
+            PreProcessing::AddPolynomial { order } => {
+                polynomial_features(x, *order).map_err(Self::feature_error_to_settings)
+            }
             PreProcessing::ReplaceWithPCA {
                 number_of_components,
-            } => {
-                self.train_pca(x, *number_of_components);
-            }
+            } => self.fit_pca(&x, *number_of_components),
             PreProcessing::ReplaceWithSVD {
                 number_of_components,
-            } => {
-                self.train_svd(x, *number_of_components);
-            }
-            _ => {}
+            } => self.fit_svd(&x, *number_of_components),
         }
     }
 
-    /// Apply preprocessing to data.
+    /// Apply preprocessing to inference data.
     pub fn preprocess(
         &self,
         x: InputArray,
         settings: &PreProcessing,
-    ) -> Result<InputArray, FeatureError> {
-        Ok(match settings {
-            PreProcessing::None => x,
-            PreProcessing::AddInteractions => interaction_features(x)?,
-            PreProcessing::AddPolynomial { order } => polynomial_features(x, *order)?,
-            PreProcessing::ReplaceWithPCA {
-                number_of_components: _,
-            } => self.pca_features(&x),
-            PreProcessing::ReplaceWithSVD {
-                number_of_components: _,
-            } => self.svd_features(&x),
-        })
+    ) -> Result<InputArray, ModelError> {
+        match settings {
+            PreProcessing::None => Ok(x),
+            PreProcessing::AddInteractions => {
+                interaction_features(x).map_err(Self::feature_error_to_model)
+            }
+            PreProcessing::AddPolynomial { order } => {
+                polynomial_features(x, *order).map_err(Self::feature_error_to_model)
+            }
+            PreProcessing::ReplaceWithPCA { .. } => self.pca_features(&x),
+            PreProcessing::ReplaceWithSVD { .. } => self.svd_features(&x),
+        }
     }
 
-    fn train_pca(&mut self, x: &InputArray, n: usize) {
+    fn fit_pca(&mut self, x: &InputArray, n: usize) -> Result<InputArray, SettingsError> {
         let pca = PCA::fit(
             x,
             PCAParameters::default()
                 .with_n_components(n)
                 .with_use_correlation_matrix(true),
         )
-        .expect("Could not train PCA preprocessor");
+        .map_err(|err| Self::failed_to_settings(&err))?;
+        let transformed = pca
+            .transform(x)
+            .map_err(|err| Self::failed_to_settings(&err))?;
         self.pca = Some(pca);
+        Ok(transformed)
     }
 
-    fn pca_features(&self, x: &InputArray) -> InputArray {
-        self.pca
+    fn pca_features(&self, x: &InputArray) -> Result<InputArray, ModelError> {
+        let pca = self
+            .pca
             .as_ref()
-            .expect("PCA model not trained")
-            .transform(x)
-            .expect("Could not transform data using PCA")
+            .ok_or_else(|| ModelError::Inference("PCA model not trained".to_string()))?;
+        pca.transform(x)
+            .map_err(|err| ModelError::Inference(err.to_string()))
     }
 
-    fn train_svd(&mut self, x: &InputArray, n: usize) {
+    fn fit_svd(&mut self, x: &InputArray, n: usize) -> Result<InputArray, SettingsError> {
         let svd = SVD::fit(x, SVDParameters::default().with_n_components(n))
-            .expect("Could not train SVD preprocessor");
+            .map_err(|err| Self::failed_to_settings(&err))?;
+        let transformed = svd
+            .transform(x)
+            .map_err(|err| Self::failed_to_settings(&err))?;
         self.svd = Some(svd);
+        Ok(transformed)
     }
 
-    fn svd_features(&self, x: &InputArray) -> InputArray {
-        self.svd
+    fn svd_features(&self, x: &InputArray) -> Result<InputArray, ModelError> {
+        let svd = self
+            .svd
             .as_ref()
-            .expect("SVD model not trained")
-            .transform(x)
-            .expect("Could not transform data using SVD")
+            .ok_or_else(|| ModelError::Inference("SVD model not trained".to_string()))?;
+        svd.transform(x)
+            .map_err(|err| ModelError::Inference(err.to_string()))
+    }
+
+    fn feature_error_to_settings(err: FeatureError) -> SettingsError {
+        SettingsError::PreProcessingFailed(err.to_string())
+    }
+
+    fn feature_error_to_model(err: FeatureError) -> ModelError {
+        ModelError::Inference(err.to_string())
+    }
+
+    fn failed_to_settings(err: &Failed) -> SettingsError {
+        SettingsError::PreProcessingFailed(err.to_string())
     }
 }
diff --git a/src/model/supervised.rs b/src/model/supervised.rs
index 198b098..78aaa98 100644
--- a/src/model/supervised.rs
+++ b/src/model/supervised.rs
@@ -11,13 +11,14 @@ use crate::model::{
     preprocessing::Preprocessor,
 };
 use crate::settings::{
-    ClassificationSettings, FinalAlgorithm, Metric, RegressionSettings, SupervisedSettings,
+    ClassificationSettings, FinalAlgorithm, Metric, RegressionSettings, SettingsError,
+    SupervisedSettings,
 };
 use comfy_table::{
     Attribute, Cell, Table, modifiers::UTF8_SOLID_INNER_BORDERS, presets::UTF8_FULL,
 };
 use humantime::format_duration;
-use smartcore::error::Failed;
+use smartcore::error::{Failed, FailedError};
 use smartcore::linalg::{
     basic::arrays::{Array, Array1, Array2, MutArrayView1},
     traits::{
@@ -111,7 +112,9 @@ where
 {
     /// Settings for the model.
     pub settings: S,
-    /// Training features.
+    /// Original training features used to recompute preprocessing steps.
+    x_train_raw: InputArray,
+    /// Preprocessed training features fed to algorithms.
     x_train: InputArray,
     /// Training targets.
     y_train: OutputArray,
@@ -136,8 +139,10 @@ where
 {
     /// Create a new supervised model.
     pub fn new(x: InputArray, y: OutputArray, settings: S) -> Self {
+        let x_train_raw = x.clone();
         Self {
             settings,
+            x_train_raw,
             x_train: x,
             y_train: y,
             comparison: Vec::new(),
@@ -152,8 +157,11 @@ where
     /// Returns [`Failed`] if cross-validation fails for any algorithm.
     pub fn train(&mut self) -> Result<(), Failed> {
         let sup = self.settings.supervised();
-        self.preprocessor
-            .train(&self.x_train.clone(), &sup.preprocessing);
+        let raw = self.x_train_raw.clone();
+        self.x_train = self
+            .preprocessor
+            .fit_transform(raw, &sup.preprocessing)
+            .map_err(|err| Self::preprocessing_failed(&err))?;
 
         for alg in <A>::all_algorithms(&self.settings) {
             let trained = alg.cross_validate_model(&self.x_train, &self.y_train, &self.settings)?;
@@ -169,10 +177,7 @@ where
     /// Returns [`ModelError::NotTrained`] if no algorithm has been trained or if inference fails.
     pub fn predict(&self, x: InputArray) -> ModelResult<OutputArray> {
         let sup = self.settings.supervised();
-        let x = self
-            .preprocessor
-            .preprocess(x, &sup.preprocessing)
-            .map_err(|e| ModelError::Inference(e.to_string()))?;
+        let x = self.preprocessor.preprocess(x, &sup.preprocessing)?;
 
         match sup.final_model_approach {
             FinalAlgorithm::None => Err(ModelError::NotTrained),
@@ -203,6 +208,10 @@ where
             self.comparison.reverse();
         }
     }
+
+    fn preprocessing_failed(err: &SettingsError) -> Failed {
+        Failed::because(FailedError::ParametersError, &err.to_string())
+    }
 }
 
 impl<A, S, InputArray, OutputArray> Display for SupervisedModel<A, S, InputArray, OutputArray>
diff --git a/src/settings/error.rs b/src/settings/error.rs
index dd71ace..d6c02d8 100644
--- a/src/settings/error.rs
+++ b/src/settings/error.rs
@@ -5,12 +5,14 @@ use std::fmt::{Display, Formatter};
 use super::Metric;
 
 /// Errors related to model settings.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub enum SettingsError {
     /// A required metric was not specified.
     MetricNotSet,
     /// The provided metric is not supported for the task.
     UnsupportedMetric(Metric),
+    /// Preprocessing configuration failed to run successfully.
+    PreProcessingFailed(String),
 }
 
 impl Display for SettingsError {
@@ -18,6 +20,9 @@ impl Display for SettingsError {
         match self {
             Self::MetricNotSet => write!(f, "a metric must be set"),
             Self::UnsupportedMetric(m) => write!(f, "unsupported metric: {m}"),
+            Self::PreProcessingFailed(msg) => {
+                write!(f, "preprocessing configuration failed: {msg}")
+            }
         }
     }
 }
diff --git a/tests/classification.rs b/tests/classification.rs
index 127bc11..01e7e4a 100644
--- a/tests/classification.rs
+++ b/tests/classification.rs
@@ -5,7 +5,7 @@ use automl::algorithms::ClassificationAlgorithm;
 use automl::model::Algorithm;
 use automl::settings::{
     BernoulliNBParameters, CategoricalNBParameters, ClassificationSettings,
-    MultinomialNBParameters, RandomForestClassifierParameters, SVCParameters,
+    MultinomialNBParameters, PreProcessing, RandomForestClassifierParameters, SVCParameters,
 };
 use automl::{DenseMatrix, ModelError, SupervisedModel};
 use classification_data::{
@@ -217,6 +217,32 @@ fn bernoulli_nb_rejects_non_binary_without_threshold() {
     );
 }
 
+#[test]
+fn classification_pca_preprocessing_predicts() {
+    type Model = SupervisedModel<
+        ClassificationAlgorithm<f64, u32, DenseMatrix<f64>, Vec<u32>>,
+        ClassificationSettings,
+        DenseMatrix<f64>,
+        Vec<u32>,
+    >;
+
+    let (x, y) = classification_testing_data();
+    let settings = ClassificationSettings::default()
+        .with_svc_settings(SVCParameters::default())
+        .with_preprocessing(PreProcessing::ReplaceWithPCA {
+            number_of_components: 2,
+        });
+
+    let mut model: Model = SupervisedModel::new(x, y, settings);
+    model.train().unwrap();
+
+    let predictions = model
+        .predict(DenseMatrix::from_2d_array(&[&[0.0, 0.0], &[1.0, 1.0]]).unwrap())
+        .expect("PCA-preprocessed model should predict successfully");
+
+    assert_eq!(predictions.len(), 2);
+}
+
 #[test]
 fn invalid_alpha_returns_error() {
     // Arrange
diff --git a/tests/regression.rs b/tests/regression.rs
index 9e9e91e..716e9b9 100644
--- a/tests/regression.rs
+++ b/tests/regression.rs
@@ -4,7 +4,7 @@ mod regression_data;
 use automl::algorithms::RegressionAlgorithm;
 use automl::model::Algorithm;
 use automl::settings::{
-    Distance, ExtraTreesRegressorParameters, KNNParameters, Kernel, SVRParameters,
+    Distance, ExtraTreesRegressorParameters, KNNParameters, Kernel, PreProcessing, SVRParameters,
     XGRegressorParameters,
 };
 use automl::{DenseMatrix, RegressionSettings, SupervisedModel};
@@ -234,6 +234,36 @@ fn test_xgboost_skiplist_controls_algorithms() {
     ));
 }
 
+#[test]
+fn regression_polynomial_preprocessing_predicts() {
+    type Model = SupervisedModel<
+        RegressionAlgorithm<f64, f64, DenseMatrix<f64>, Vec<f64>>,
+        RegressionSettings<f64, f64, DenseMatrix<f64>, Vec<f64>>,
+        DenseMatrix<f64>,
+        Vec<f64>,
+    >;
+
+    let (x, y) = regression_testing_data();
+    let settings = RegressionSettings::default()
+        .with_preprocessing(PreProcessing::AddPolynomial { order: 2 })
+        .only(&RegressionAlgorithm::default_knn_regressor());
+
+    let mut regressor: Model = SupervisedModel::new(x, y, settings);
+    regressor.train().unwrap();
+
+    let predictions = regressor
+        .predict(
+            DenseMatrix::from_2d_array(&[
+                &[234.289, 235.6, 159.0, 107.608, 1947., 60.323],
+                &[259.426, 232.5, 145.6, 108.632, 1948., 61.122],
+            ])
+            .unwrap(),
+        )
+        .expect("Polynomial preprocessing should allow prediction");
+
+    assert_eq!(predictions.len(), 2);
+}
+
 fn test_from_settings(settings: RegressionSettings<f64, f64, DenseMatrix<f64>, Vec<f64>>) {
     // Set up the regressor settings and load data
     type Model = SupervisedModel<