We report three cases of frozen shoulder (including one with bilateral involvement) in human immunodeficiency virus (HIV)-positive patients under triple antiretroviral therapy. In each case, the diagnosis was confirmed by arthrography, and the classic causes of frozen shoulder were ruled out. We suggest that protease inhibitor therapy may have contributed to the development of frozen shoulder in these patients. Long-term follow-up of the increasing numbers of patients under triple antiretroviral therapy will confirm or refute this hypothesis.