We report the results of Brunelli's abductor pollicis longus transfer for symptomatic instability of the trapeziometacarpal joint in 15 hands (14 patients) at a mean follow-up of 21 months. Patients were assessed subjectively, and objectively by an independent observer. All but one of the patients were very satisfied with the result of the operation, including the six patients who had significant degeneration of the carpometacarpal joint surface preoperatively. Four patients said they had no pain and the mean pain score overall on a visual analogue scale was 1.2 (out of a maximum of 10). Overall the outcome was rated good or excellent in 11 of the 15 thumbs.