Obsessive-compulsive symptoms (OCSs) frequently occur in schizophrenia and seem to worsen prognosis. Many case studies suggest that OCSs appear or worsen with an atypical antipsychotic agent treatment (that is, with risperidone, olanzapine, and clozapine). Therefore, family or personal history of OCS should be investigated before initiating such treatment, and OCS onset should be monitored during treatment. Clozapine is involved in most such cases. When OCSs appear with clozapine, dosage can be reduced and a serotonin reuptake inhibitor treatment added. Current studies suggest that patients with schizophrenia and OCSs should benefit from treatment with an antipsychotic and an antiobsessive medication. Two controlled trials deal with OCS treatment in schizophrenia: the first, with clomipramine; and the second, with fluvoxamine. Both have proven their efficacy, but these trials include a small number of patients with heterogeneous characteristics.