Obsessive-Compulsive (OC) symptoms are observed in a substantial proportion of schizophrenic patients and pose a significant therapeutic challenge. Based on findings of the benefit of the anti-obsessive agent clomipramine, we designed an open-label study to examine the effect of adding the serotonin-selective reuptake inhibitor (SSRI) fluvoxamine to the ongoing antipsychotic regimen of schizo-obsessive patients. The study population consisted of ten neuroleptic-stabilized chronic schizophrenic patients with OC symptoms. Fluvoxamine (up to 150 mg/day) was added to the ongoing antipsychotic treatment, which remained unchanged for the entire 12-week trial period. The patients were evaluated before the trial and at weeks 1, 2, 4, 6, 8 and 12 (end point) with the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), the Schedule for Assessment of Positive Symptoms and the Schedule for Assessment of Negative Symptoms. The results showed a significant improvement in obsessions (P < 0.02) (but not compulsions) and both positive (P < 0.01) and negative (P < 0.05) schizophrenic symptoms. By the end of the trial, three patients showed a more than 50% reduction in the Y-BOCS score, with complete amelioration of the OC symptoms in one of them. Three patients were dropped from the study during the first 4 weeks, two because of aggressiveness and one because of psychotic exacerbation. No exacerbation or new onset of extrapyramidal side-effects (EPS), as measured by the Barnes Akathisia Scale (BARS) and the Simpson-Angus Scale (SAS), was noted during the course of the trial and there were no other significant clinical side-effects of fluvoxamine addition. We conclude that fluvoxamine may be an effective adjunctive agent in some schizo-obsessive patients.