Weber's internal rotation osteotomy of the humeral head is recommended for the treatment of anteroinferior shoulder instability with a large Hill-Sachs defect. The observation of severe joint degeneration in the course of long-term follow-up provided the motivation for this study. An osteotomy was performed in 42 patients from 1984 to 1990. Thirty-four patients were available for clinical and radiological follow-up after 14.5 years. Our own CT-based classification was applied to categorize the degree of osteoarthritis. A shoulder prosthesis was implanted in 9 patients (26%). Only 3 patients (9%) did not show any signs of degeneration. A statistically significant relationship was found between increased internal rotation of the humeral head and disease severity (P = .03). A lower incidence of joint degeneration (P = .02) was found for patients with generalized ligamentous laxity. We therefore recommend this osteotomy only as a salvage procedure whereby the internal rotation of the humeral head should not exceed 20 degrees .