A prospective arthroscopic study was conducted on 31 patients with an acute first-time anterior shoulder dislocation (AFASD). The patients were aged between 16 and 39 years. The mean age was 24 years. None had a history of shoulder problems. All were evaluated after 1, 2, and 5 years. The Constant score, Rowe score, recurrence rate, and instability rate were evaluated, as well as patient satisfaction and sports participation. We conclude that after a prolonged follow-up, an increase in the instability rate in young patients with AFASD may become apparent. The overall instability rate was 55% (17/31) after 5-year follow-up. In patients aged younger than 18 years the instability rate was 71% (5/7). Age was the only predictive factor in shoulder instability. The mean Rowe score was 87 (range, 57-100; SD, 14). Three patients had undergone a stabilization operation at the 5-year follow-up. The intraarticular pathology found at arthroscopy was not predictive of shoulder instability. We could not find a correlation between sporting activities and shoulder instability. On the basis of our results, it appears unlikely that arthroscopic lavage reduces redislocation rates after AFASD in the young patient.