An eight-week double-blind, multicentre study was performed to evaluate the efficacy and safety of sertraline vs. fluoxetine in the treatment of major depression (DSM-III-R). There were 108 out-patients, from nine Italian centres, entered into the study, of whom 88 were evaluable (48 sertraline, 40 fluoxetine). The final mean daily dose of sertraline was 72 mg and for fluoxetine it was 28 mg. Both treatment groups showed a statistically significant improvement from baseline at one week, and this was maintained until the end of treatment for all of the following measures: Hamilton Rating Scales for Depression and Anxiety, the Montgomery Asberg Depression Rating Scale, Clinical Global Impressions Scale, Zung Self-Rating Scale for Anxiety and the Leeds Sleep Evaluation Questionnaire. Although there was a numerical advantage for sertraline on several efficacy measures, there was no statistically significant difference found between the treatment groups. The incidence of adverse events was similar for both treatments; 40.4% for sertraline and 39.3% for fluoxetine. However, adverse events were generally rated by patients as of lower severity in the sertraline group. In addition, for the fluoxetine group, there was a higher incidence of agitation, anxiety and insomnia than for sertraline. Sertraline was considered to be better tolerated than fluoxetine overall, since only 9.6% of sertraline-treated patients discontinued treatment due to therapy failure whereas in the fluoxetine-treated group this figure was 19.6%. By contrast, 13.5% of sertraline-treated patients discontinued prematurely because of clinical improvement, compared with 10.7% of fluoxetine-treated patients.