diff --git a/optimas/core/trial.py b/optimas/core/trial.py
index 6879cb32..94d3877f 100644
--- a/optimas/core/trial.py
+++ b/optimas/core/trial.py
@@ -36,10 +36,6 @@ class Trial:
         parameter).
     index : int, optional
         Index of the trial.
-    custom_parameters : list of TrialParameter, optional
-        Additional parameters needed to identify or carry out the trial, and
-        which will be included in the optimization history.
-
     """
 
     def __init__(
@@ -50,7 +46,6 @@ def __init__(
         parameter_values: Optional[List[float]] = None,
         evaluations: Optional[List[Evaluation]] = None,
         index: Optional[int] = None,
-        custom_parameters: Optional[List[TrialParameter]] = None,
     ) -> None:
         # Process inputs.
         self._varying_parameters = varying_parameters
@@ -63,16 +58,9 @@ def __init__(
         )
         evaluations = [] if evaluations is None else evaluations
         self._index = index
-        self._custom_parameters = (
-            [] if custom_parameters is None else custom_parameters
-        )
         self._ignored = False
         self._ignored_reason = None
 
-        # Add custom parameters as trial attributes.
-        for param in self._custom_parameters:
-            setattr(self, param.name, None)
-
         # Create map of evaluations to objectives and analyzed parameters.
         self._mapped_evaluations = {}
         for par in self._objectives + self._analyzed_parameters:
@@ -139,11 +127,6 @@ def ignored_reason(self) -> str:
         """Get the reason why the trial is ignored by the generator."""
         return self._ignored_reason
 
-    @property
-    def custom_parameters(self) -> List[TrialParameter]:
-        """Get the list of custom trial parameters."""
-        return self._custom_parameters
-
     @property
     def status(self) -> TrialStatus:
         """Get current trial status."""
diff --git a/optimas/gen_functions.py b/optimas/gen_functions.py
index c3e37eb3..3b08c33f 100644
--- a/optimas/gen_functions.py
+++ b/optimas/gen_functions.py
@@ -78,9 +78,6 @@ def persistent_generator(H, persis_info, gen_specs, libE_info):
             if "task" in H_o.dtype.names:
                 H_o["task"][i] = trial.trial_type
                 run_params = run_params[trial.trial_type]
-            if trial.custom_parameters is not None:
-                for par in trial.custom_parameters:
-                    H_o[par.save_name][i] = getattr(trial, par.name)
             H_o["trial_index"][i] = trial.index
             H_o["num_procs"][i] = run_params["num_procs"]
             H_o["num_gpus"][i] = run_params["num_gpus"]
diff --git a/optimas/generators/base.py b/optimas/generators/base.py
index 931a64e1..2a33957a 100644
--- a/optimas/generators/base.py
+++ b/optimas/generators/base.py
@@ -211,7 +211,6 @@ def ask(self, n_trials: int) -> List[Trial]:
                         varying_parameters=self._varying_parameters,
                         objectives=self._objectives,
                         analyzed_parameters=self._analyzed_parameters,
-                        custom_parameters=self._custom_trial_parameters,
                     )
                 )
             # Ask the generator to fill them.
@@ -489,7 +488,6 @@ def _create_trials_from_external_data(
                 ],
                 objectives=self._objectives,
                 analyzed_parameters=self._analyzed_parameters,
-                custom_parameters=self._custom_trial_parameters,
             )
             for par in self._custom_trial_parameters:
                 setattr(trial, par.name, trial_data[par.save_name][i])