CONTEXT: Osteoporotic fractures are common among elderly men. OBJECTIVE: To evaluate among older men the cost-effectiveness of bone densitometry followed by 5 years of oral bisphosphonate therapy to prevent fractures for those found to have osteoporosis (femoral neck T score < or =-2.5), compared with no intervention. DESIGN, SETTING, AND POPULATION: Computer Markov microsimulation model using a societal perspective and a lifetime horizon. Simulations were performed for hypothetical cohorts of white men aged 65, 70, 75, 80, or 85 years, with or without prior clinical fracture. Data sources for model parameters included the Rochester Epidemiology Project for fracture costs and population-based age-specific fracture rates; the Osteoporotic Fractures in Men (MrOS) study and published meta-analyses for the associations among prior fractures, bone density, and incident fractures; and published studies of fracture disutility. MAIN OUTCOME MEASURES: Costs per quality-adjusted life-year (QALY) gained for the densitometry and follow-up treatment strategy compared with no intervention, calculated from lifetime costs and accumulated QALYs for each strategy. RESULTS: Lifetime costs per QALY gained for the densitometry and follow-up treatment strategy were less than $50,000 for men aged 65 years or older with a prior clinical fracture and for men aged 80 years or older without a prior fracture. These results were most sensitive to oral bisphosphonate cost and fracture reduction efficacy, the strength of association between bone mineral density and fractures, fracture rates and disutility, and medication adherence. CONCLUSIONS: Bone densitometry followed by bisphosphonate therapy for those with osteoporosis may be cost-effective for men aged 65 years or older with a self-reported prior clinical fracture and for men aged 80 to 85 years with no prior fracture. This strategy may also be cost-effective for men as young as 70 years without a prior clinical fracture if oral bisphosphonate costs are less than $500 per year or if the societal willingness to pay per QALY gained is $100,000.