Objective: To investigate the association between pemphigus and osteoporosis. Design: Case-control study. Setting: A large health care provider organization in Israel. Participants: Patients with pemphigus older than 20 years (hereinafter, pemphigus patients) were compared with a sample of age- and sex-matched controls. Interventions: Data retrieval from a large community-based medical database regarding health-related lifestyles, comorbidities, use of medications, bone mineral density scans, and drugs for osteoporosis. Main Outcome Measures: The prevalence of osteoporosis in patients and controls, use of bone mineral density scans, and drugs for osteoporosis. Results: The study included 255 pemphigus patients and 509 controls older than 20 years. Osteoporosis was diagnosed among 40.4% of pemphigus patients compared with 6.5% of controls (P<.001; odds ratio [OR], 9.77; 95% confidence interval [CI], 6.34-15.10). After controlling for confounders, including age, sex, and duration of glucocorticosteroid therapy and proton pump inhibitor therapy, the associations with osteoporosis persisted (OR, 4.27; 95% CI, 2.44-7.47; P<.001). Similar results were obtained when using cumulative glucocorticosteroid dose. Only 73 pemphigus patients with osteoporosis (70.9%) had undergone a bone mineral density test within the past 10 years. While most pemphigus patients with osteoporosis purchased medications for osteoporosis, including calcium (95.1% of patients), cholecalciferol (89.3%), bisphosphonates (90.3%), or raloxiphene (8.8%), the duration of therapy was short. Conclusions: We found an association between pemphigus and osteoporosis, which persisted after controlling for glucocorticosteroid use. Monitoring and treatment of osteoporosis in pemphigus patients was suboptimal in this study.