Background: Depression is common in later life. Aims: To determine whether exercise is effective as an adjunct to antidepressant therapy in reducing depressive symptoms in older people. Method: Patients were randomised to attend either exercise classes or health education talks for 10 weeks. Assessments were made ‘blind’ at baseline, and at 10 and 34 weeks. The primary outcome was seen with the 17-item Hamilton Rating Scale for Depression (HRSD). Secondary outcomes were seen with the Geriatric Depression Scale, Clinical Global Impression and Patient Global Impression. Results: At 10 weeks a significantly higher proportion of the exercise group (55% v. 33%) experienced a greater than 30% decline in depression according to HRSD (OR=2.51, P=0.05, 95% CI 1.00-6.38). Conclusions: Because exercise was associated with a modest improvement in depressive symptoms at 10 weeks, older people with poorly responsive depressive disorder should be encouraged to attend group exercise activities.