Ulnar collateral ligament injury of the elbow in throwing athletes is a common occurrence, and either operative or nonoperative treatment is an option. The results of operative repairs and reconstructions have been well documented in the literature; however, little information has been reported on the outcome of nonoperative treatment. From 1994 to 1997, we evaluated 31 throwing athletes with ulnar collateral ligament injuries. The purpose of this study was to determine what percentage of athletes could return to their sport without surgical intervention and to identify factors that would predict return to full competition by an athlete treated nonoperatively. The factors studied included acute versus insidious onset of symptoms, the duration of symptoms before treatment, and age. Nonoperative treatment, which included a minimum of 3 months' rest with rehabilitation exercises, allowed 42% of the athletes in our study (N = 13) to return to their previous level of competition. Those who did return did so at an average of 24.5 weeks after diagnosis. No predictive findings obtained either through the patient's history or physical examination were found that would assist the clinician or athlete in predicting the success of nonoperative treatment.