The aim of this study was to evaluate the efficacy, safety, and tolerability of weekly alendronate administration on male osteoporosis in Taiwan. This 6-month, randomized, open-label controlled trial enrolled 46 men with osteoporosis who were randomized to either 70 mg alendronate once weekly (n = 23) or control (n = 23). Bone mineral density (BMD) of lumbar spine and hip and biochemical bone turnover markers were measured; adverse events and tolerability were assessed. Subjects treated with alendronate showed a significant increase in BMD of 5.5% (vs. 2% in control group) at the lumbar spine and 2.7% (vs. 0.7%) at the femoral neck (P < 0.05) at 6 months, respectively. There were also significant decreases in serum level of bone formation marker (bone-specific alkaline phosphatase) and urinary excretion of bone resorption marker (deoxypyridinoline) at 3 and 6 months. Thus, alendronate showed anti-osteoporotic effects by increasing BMD and decreasing the concentrations of bone markers. The adverse events were mild and showed no significant difference between the two groups on safety assessments.