Introduction. We compare the prevalence of obsessive-compulsive symptoms in schizophrenic patients in treatment with clozapine and those who receive classic antipsychotic drugs. Method. Outpatients with schizophrenia treated with clozapine (n = 56) or classic antipsychotic drugs (n = 54) at the Honorio Delgado-Hideyo Noguchi Specialized Institute in Mental Health (Lima-Peru), were evaluated for the presence of obsessive-compulsive symptoms by means of the Obsessive-Compulsive Disorder Module of Structured Clinical Interview for DSM-IV and Yale-Brown Obsessive-Compulsive Symptoms Checklist. Results. 46.4% of patients treated with clozapine presented obsessive-compulsive symptoms while this occurred in 20.4% of those with classic antipsychotic drugs (p = 0.005). In addition, 21.4% of patients with clozapine and 13% of those treated with classic antipsychotics presented obsessive-compulsive disorder according to DSM-IV criteria (p = 0.31). Conclusion. In schizophrenic patients, treatment with clozapine is associated with a higher rate of obsessive-compulsive symptoms than treatment with classic antipsychotic drugs.