Interest in the association of obsessive-compulsive (OC) symptoms and schizophrenia has been reawakened since the introduction of clozapine for treatment of schizophrenia. We describe the appearance of this disorder and examine the efficacy of adding fluvoxamine to ongoing clozapine treatment of the OC and schizophrenic symptoms. Four patients with DSM-III-R schizophrenic disorder, in whom OC symptoms appeared during the course of clozapine treatment, are reported. In two patients, fluvoxamine, a serotonin-selective reuptake inhibitor (SSRI), was added to clozapine under open-trial conditions. The patients were serially assessed by using the Brief Psychiatric Rating Scale, Yale-Brown Obsessive-Compulsive Scale, and Scale for the Assessment of Negative Symptoms. The de novo occurrence and eventual spontaneous reduction of OC symptoms were noted in two schizophrenic patients treated with clozapine. In the other two patients, one with previous and the other with a family history of OC disorder, the addition of fluvoxamine to clozapine was effective in eliminating the OC symptoms. A concomitant improvement in the schizophrenic symptomatology was seen as well. It appears that disabling OC symptoms may occur as in response to clozapine treatment in chronic drug-resistant schizophrenic patients. Some of the latter may benefit from the addition of an SSRI to the ongoing clozapine regimen.