OBJECTIVE: Time to treatment discontinuation for any cause was previously identified as an important outcome parameter in the medication management of schizophrenia. This study compared four antipsychotics - olanzapine, risperidone, quetiapine, and haloperidol - on the time to all-cause discontinuation. METHODS: Participants (N=964) were new initiators of olanzapine, risperidone, quetiapine or haloperidol in the Schizophrenia Care and Assessment Program (SCAP), a 3-year longitudinal, observational study of schizophrenia. Time to all-cause discontinuation of the antipsychotic during the 1 year following its initiation was measured by a) the total number of days on the antipsychotic, and b) the number of days of continuous treatment up to the first gap of >14 days. Analyses employed Mantel-Haenszel and Cox proportional hazard model. Results were further confirmed using a mixed model approach. RESULTS: Olanzapine-treated patients were on their medication significantly longer than patients receiving risperidone, quetiapine, or haloperidol. Compared with olanzapine, the likelihood of discontinuation was 26%, 54%, and 158% greater among patients receiving risperidone, quetiapine, or haloperidol, respectively. CONCLUSION: Antipsychotics were found to significantly differ in the time to all-cause discontinuation, such that olanzapine-treated patients evidenced the longest time to discontinuation, followed by risperidone, quetiapine, and haloperidol.