Obsessive-compulsive symptoms (OCS) have been observed in a substantial proportion of schizophrenic patients. In this study, the rate of occurrence of OCS and obsessive-compulsive disorder (OCD) in schizophrenic patients, and also the interrelationship between OCS and schizophrenic symptoms and depressive symptoms were assessed. A total of 100 subjects with a diagnosis of schizophrenia from the 4th edition of the Diagnostic and Statistical Manual (DSM-IV) were evaluated by the structured and clinical interview for axis-1 DSM-IV disorders-patient edition (SCID-P), the Positive and Negative Syndrome Scale (PANSS), Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), and the Calgary Depression Rating Scale for Schizophrenia. The prevalance of OCS in individuals meeting criteria for schizophrenia was 64%. A total of 30 of these patients (Y-BOCS total score > or =7) also met the DSM-IV criteria for OCD. The total score on Y-BOCS was significantly correlated with total score on PANSS, Positive-PANSS score, General-PANSS score and total score on Calgary Depression Rating Scale for Schizophrenia. OCS and OCD relatively frequent in schizophrenic patients and OCS are significantly correlated with the severity of psychosis, positive symptoms, and depressive symptoms in schizophrenic patients. These findings provide further evidence for the importance of OCS in schizophrenia.