In a double-blind multicentre trial in patients with major depression, the ecacy and the tolerability of sertraline were compared to those of imipramine, during an 8-week acute treatment phase followed by a 16-week continuation treatment phase in treatment responders. A total of 104 patients who met DSM-III-R criteria for major depression, HAM-D 17-item518 and Raskin Depression score > Covi Anxiety score, were randomized to receive either sertraline or imipramine. The initial daily dosage of 50 mg of sertraline or imipramine was rapidly titrated upwards in increments of 50 mg/day at weekly intervals, tolerability permitting, to a maximum of 200 mg/day by the fourth week. Eighty-eight patients completed at least 3 weeks of treatment and were included in the ecacy evaluable population. Both treatment groups demonstrated similar improvements on depression and anxiety rating scales during acute treatment, however, sertraline demonstrated signi®cantly more improvement relative to imipramine on the HAM-D and Covi Anxiety scales after 1 week of treatment. Sertraline was more eective (HAM-D 17-item, CGI-S, SCL-56 Total score, SCL-56 Depression score, Covi Anxiety score) than imipramine in reducing depressive symptoms at the end of 24 weeks of treatment. There were signi®cant improvements in all rating scales at week 24 relative to week 8 in the sertraline group but not in the imipramine group. The SCL-56 Total score, SCL-56 Depression score, Raskin Depression score and Covi Anxiety score at week 24 relative to week 8 showed signi®cantly greater improvement in the sertraline group compared to the imipramine group. Imipramine was associated with a signi®cantly higher incidence of dry mouth, sweating, constipation, palpitations, and a signi®cantly higher heart rate and blood pressure. Sertraline was associated with a signi®cantly higher incidence of diarrhoea/loose stools and insomnia. This study demonstrated a faster onset of therapeutic eect for sertraline relative to imipramine, re¯ecting the initiation of sertraline in a therapeutic dose of 50 mg/day and the need for gradual titration of imipramine to a therapeutic dose, at the beginning of treatment. Although ecacy was similar in both treatment groups at the end of the 8 weeks of acute therapy, sertraline-treated patients continued to manifest gradual improvements in depressive and anxiety symptoms during the 16 weeks of continuation therapy such that sertraline-treated patients were signi®cantly more improved at the end of 24 weeks of therapy.