To compare the effects of typical and atypical antipsychotic drugs on sleep activity and subjective sleep quality. Design Randomised, double-blind, placebo-controlled, four-period cross-over, clinical trial was used to evaluate the effects of active treatments on objective and subjective sleep variables. Setting Sleep laboratory evaluation. Participants Twenty healthy young volunteers, both sexes. Interventions Single oral morning administrations of olanzapine 5 mg, risperidone 1 mg, haloperidol 3 mg and placebo.