The efficacy and tolerability of sertraline in 422 out-patients with major depression (DSM-III-R) was evaluated in an open multicentre 8-month study. Patients received sertraline 50 mg/day; if there was insufficient response at week 4, the dose was increased to 100 mg/day. After 8 weeks, 68.6% of patients had responded (> or = 50% reduction in Montgomery Asberg depression rating scale and clinical global impression scale scores of two or less (improvement of illness) and three or less (severity of illness); of patients receiving continuation treatment, 87.9% maintained at least a partial response at the final visit. The clinical response to the 50 mg/day dose was maintained throughout the acute treatment in 64% of patients. In all, 23% of the patients had mild or moderate drug-related gastrointestinal disturbances, which generally disappeared after 2 weeks. Only 8% of the patients withdrew because of side-effects. Just over half of the patients were taking other psychotropic drugs. Nevertheless the results of this open study are consistent with those of controlled studies in which sertraline was effective and well tolerated, in acute and continuation treatment for major depression, at 50 mg/day in most patients.