Clozapine and olanzapine are antipsychotic drugs commonly used to treat schizophrenia and psychosis; however, few studies have investigated their effects on cognitive function using animal models. Thus, the effects of olanzapine and clozapine on memory acquisition, consolidation and retrieval were investigated in naive mice using a modified elevated plus maze (mEPM) task. Olanzapine (0.15 and 0.30 mg/kg) and clozapine (0.5 and 1 mg/kg) were injected intraperitoneally (i.p.) into male Balb-c mice before training, immediately after training or before the second day of the trial. Our results showed that both olanzapine and clozapine disrupted the acquisition of spatial memory. In addition, clozapine impaired the consolidation of spatial memory, while olanzapine had no effect. Furthermore, olanzapine and clozapine significantly disrupted memory retrieval in naive mice. Thus, these results at least suggest that olanzapine can be a superior treatment for schizophrenia compared to clozapine. (C) 2011 Elsevier Ireland Ltd. All rights reserved.