The objective of this study was to estimate the annual direct medical costs of osteoporosis and osteoporotic fractures incurred by French men =<50 years of age. Costs were assessed from a societal perspective for 1999 and expressed in Euros. An expert panel was consulted to identify fractures attributable to osteoporosis according to International Classification of Diseases (ICD)-10 codes. Available age- and gender-specific osteoporosis attribution probabilities (OAP) were used to derive the proportion of health-care utilization for fractures resulting from osteoporosis. Hospital and ambulatory care costs due to fractures were obtained from French databases. A total of 23,260 acute hospitalizations were found to be caused by osteoporosis, 52% of which are for hip fractures. Mean cost per stay varied widely according to the site of fracture, from Euro 1300 (wrist fracture) to Euro 5900 (hip fracture). Consequently, the total cost of acute hospitalization amounts to Euro 97.6 million, with hip fractures accounting for 73.2% of the expenditures. Rehabilitation and convalescence costs were estimated to be Euro 90.8 million, generating a total hospital cost of Euro 188.4 million. The total outpatient costs were estimated to be Euro 9.1 million. Thus, the total medical costs of male osteoporosis amount to Euro 197.5 million. A sensitivity analysis was performed to test the robustness of this figure. We estimate the number of fractures by applying international incidence rates from the literature to the French male population aged =<50 years, whereas the OAP and unit costs were kept constant. This approach yielded an estimate of 21,857 fractures, which is only 6% below the base case. When compared with values from other countries, our study results appear very conservative.