Antidepressant therapy in the elderly age group is frequently complicated by medical comorbidity, polypharmacy and increased sensitivity to drug effects. A nonblind, noncomparative, observational, multicentre study over 8 weeks was conducted to assess the effectiveness and tolerability of sertraline (50-200 mg/day) in 1437 elderly depressed outpatients with a mean (S.D.) age of 68 (6.3) years (range 60-92) in routine clinical practise. Depressive symptoms were monitored using the Montgomery 9sberg Depression Rating Scale (MADRS) at baseline and at weeks 2, 4, 6 and 8. The mean dose of sertraline at the final visit was 85.2 mg/day (48% of patients were given the initial dose throughout the study). At the end of the study, mean percentage change of MADRS score from baseline was 61% (P<0.001). A ≥50% decrease in MADRS score was obtained in 70% of patients. Sertraline was well tolerated. Side effects occurred in 23% of patients, although only 5.1% withdrew because of adverse events. There were no significant differences in the antidepressant effectiveness or occurrence of side effects when patients with and without concomitant pathologic conditions or with and without concurrent medications were compared. These findings indicate the absence of clinically important drug interaction and confirm the effectiveness and safety of sertraline in routine clinical practise for treating elderly depressed outpatients.