Between 1980 and 1997, 27 patients underwent shoulder arthroplasty because of pain or functional impairment due to a proximal humeral nonunion. Twenty-five of the 27 shoulders with a mean 6-year follow-up period (range, 2-15 years) were included in the study. There were 19 women and 6 men, with a mean age of 65 years. The most frequent original fracture types were 2-part surgical neck (64%) and 3-part greater tuberosity fractures (28%). Twenty-one shoulders underwent hemiarthroplasty, and 4 underwent total shoulder arthroplasty. Shoulder arthroplasty resulted in significant pain relief, with mean pain scores decreasing from 4.6 to 1.8 points (P <.05). Mean active elevation improved from 41 degrees preoperatively to 88 degrees postoperatively (P <.05), and mean external rotation from 22 degrees to 38 degrees (P =.045). In 11 shoulders the greater tuberosity resorbed or was nonunited. Two of the 25 shoulders required another operation after the arthroplasty: one for periprosthetic humeral fracture and one for instability. Twenty shoulders were much better or better, and 5 were the same or worse. On the basis of a modified Neer result rating system, there was 1 excellent result, 11 satisfactory results, and 13 unsatisfactory results. Patients who have significant functional impairment from a nonunion of the humeral surgical neck with failed internal fixation, severe osteoporosis, cavitation of the humeral head, or secondary osteoarthritis may benefit from shoulder arthroplasty. Although function is not completely restored, pain relief and high levels of subjective satisfaction can be achieved.