The aim of this study was to investigate whether obsessive-compulsive patients previously treated successfully with clomipramine or fluvoxamine could tolerate reduction of the daily dosage without worsening of the clinical condition. Thirty informed obsessive-compulsive patients, given a diagnosis according to DSM-III-R criteria, were recruited consecutively into the study. Patients were blindly assigned to one of the groups of treatment with different rates of reduction of the previously effective daily drug dosage: group 1 (control group, no reduction), group 2 (reduction of 33-40%), and group 3 (reduction of 60-66%). The entire study lasted 102 days. From baseline to the end of the study, the clinical condition was evaluated by the administration of standardized tests (Yale-Brown Obsessive-Compulsive Scale, Hamilton Rating Scale for Depression, Clinical Global Impression [CGI] scale), and blood samples were collected for plasma drug level determinations. The criterion for discontinuation of the study was the worsening of obsessive-compulsive symptoms, arbitrarily defined by an increase of > 5% from the baseline total Yale-Brown Obsessive-Compulsive Scale score, as measured in two successive assessments, and a worsening of global clinical condition as measured by the CGI scale. The main result of the study was borne out from the survival analysis. There were no significant differences in the cumulative proportion of patients from each group of treatment who did not worsen during the 102 days of observation. This preliminary result, which needs to be confirmed in larger samples, suggests that long-term maintenance therapy for obsessive-compulsive disorder might be provided with lower dosages of the antiobsessional drug, with clear advantages for tolerability and compliance.