BACKGROUND: It is uncertain whether higher doses of selective serotonin reuptake inhibitors have greater efficacy in generalised anxiety disorder. AIMS: To assess the efficacy of different doses of escitalopram in generalised anxiety disorder. METHOD: Randomised, double-blind, placebo-controlled, fixed-dose, parallel-group, 12-week study, with 681 patients: placebo (n=139); escitalopram, 5 mg/day, (n=134); 10 mg/day (n=136); 20 mg/day (n=133); paroxetine, 20 mg/day (n=139). RESULTS: Mean change in the primary efficacy measure was greater with escitalopram 10 and 20 mg than with placebo; 10 mg was more efficacious than paroxetine. Paroxetine was superior to placebo on some secondary measures, at some time points. Compared with placebo, more patients withdrew because of adverse events with escitalopram 20 mg and paroxetine. CONCLUSIONS: Escitalopram was efficacious in generalised anxiety disorder, 20 was not significantly superior to 10 mg/day. Escitalopram 10 mg was more efficacious than paroxetine.