A total of 112 first ribs in 103 patients were resected over 11 years for thoracic outlet syndrome. Seventy-seven patients (84 operations) were followed up for 2.5 years or more to assess the long term results of this procedure and the factors affecting them. One month after surgery 52 per cent of limbs were asymptomatic and 77 per cent were at least improved. A follow-up examination was performed, on average 6.1 years after the operation, by two independent examiners. This evaluation showed a permanent success rate of 37 per cent among 84 limbs examined. These long term results compare unfavourably with previously published data. The reason for the poor final outcome seemed to be difficulty in selecting patients for the operation. This was not aided by any of the preoperative tests. Patients in this study were evaluated by independent examiners, and only a total absence of preceding symptoms was accepted as the criterion for success. We emphasize the importance of unbiased evaluation and long term follow-up.