A prospective randomized study was performed on 30 consecutive patients with traumatic primary anterior shoulder dislocation to compare treatment results of arthroscopic lavage with results of conventional nonoperative treatment. The patients were between 18 and 30 years of age and had no history of shoulder problems. At the 2-year follow-up, 3 (20%) of 15 patients in the lavage group had a redislocated shoulder compared with 9 (60%) of 15 patients in the nonoperative group (P = .03). Two of the patients in the lavage group compared with 6 of the patients in the control group had been operated on or were scheduled for stabilizing surgery. Functional outcome according to the Constant and Rowe shoulder scores did not reveal any significant difference (P = .07) between the groups. However, by the Rowe classification 2 of 15 patients in the lavage group had poor results versus 8 of 15 in the control group, indicating an advantage for the lavage treatment. The study showed that arthroscopic lavage reduced the risk for recurrent dislocation when compared with nonoperative treatment.