Eighty-five women with an overactive bladder enrolled in this randomised, placebo-controlled trial. Women were randomly assigned to receive either an acupuncture treatment expected to improve their bladder symptoms or a placebo acupuncture treatment designed to promote relaxation. They underwent cystometric testing, completed a 3-day voiding diary and completed the urinary distress inventory and incontinence impact questionnaire and validated quality-of-life inventories before and after 4 weekly acupuncture treatments. The primary endpoint was the number of incontinent episodes over 3 days. Secondary endpoints included voiding frequency and urgency, cystometric bladder capacity, maximum voided volume, and the urinary distress inventory and incontinence impact questionnaire symptom scores. Seventy-four women completed all aspects of the study. Women in both treatment and placebo groups had significant decreases in the number of incontinent episodes (59% for treatment, 40% for placebo) without a significant difference in the change between the groups. Women in the treatment group had a 14% reduction in urinary frequency, a 30% reduction in the proportion of voids associated with urgency and a 13% increase in both maximum voided volume and maximum cystometric capacity. Both groups also had an improvement in the urinary distress inventory and incontinence impact questionnaire scores (54% decrease for treatment, 30% decrease for placebo).