We reviewed the performance of 22 shoulder implant arthroplasties in 19 patients age 50 or younger at surgery. Patients were evaluated by telephone interview, written questionnaire, and radiographic examination. The average age at surgery was 38.6 years, and the average follow-up was 5.6 years. Patients were grouped by disease process (rheumatoid arthritis [RA], avascular necrosis [AVN], trauma, and hemophilic arthropathy [HA]) and type of prosthesis (total vs. hemiarthroplasty). The highest scores (best shoulder function) were seen in patients with hemiarthroplasty for HA. Patients with hemiarthroplasty for trauma and AVN scored similarly, whereas those with a hemiarthroplasty for RA scored lowest. Patients with RA who had a total shoulder arthroplasty scored higher than patients with hemiarthroplasty. When patients in our population with longer follow-up were compared with those with a shorter follow-up, no downward trends in shoulder function were seen. Accelerated deterioration of function of shoulder arthroplasties was not observed in our young patient population.