Objective To systematically review the efficacy and adverse events of alendronate on bone mineral density and fractures in men with osteoporosis. Methods We electronically searched MEDLINE (1990 to 2005), EMBASE (1990 to 2005), The Cochrane Library (Issue 3, 2005), Controlled Trials Register and The National Research Register, CBM disc, VIP, and CNKI. We also handsearched some related journals. The search was conducted in Nov., 2005. The quality of included randomized controlled trials (RCTs) was evaluated and meta-analysis was conducted by RevMan 4.2.8. Results We identified 7 studies including 817 patients. Sufficient evidence showed that alendronate plus calcium was superior as preventive treatment to calcium in increasing the bone mineral density (SMD 0.59, 95% CI 0.15 to 1.03, P=0.009) of the lumbar spine. The incidence of withdrawal and lost to follow-up due to adverse events of the alendronate plus calcium was lower than that of calcium (RR 0.32, 95% CI 0.11 to 0.87). Two studies showed that alendronate was superior to placebo in increasing the bone mineral density in men with osteoporosis but with no significantly statistical difference in reducing fractures. Two studies showed alendronate was superior to alfacalcidol in increasing the bone mineral density and reducing the vertebral fractures in men with osteoporosis. One study showed alendronate was not superior to calcitonin or alfacalcidol in increasing the bone mineral density in men at high risk of osteoporosis. One study comparing anledronate or parathyroid hormone with combination of these drugs in men with osteoporosis suggested that anledronate wasn’t superior to parathyroid hormone in increasing the bone mineral density, and the combination did not show any difference compared to parathyroid hormone alone. Conclusions Alendronate is more effective in prevention and treatment of men with osteoporosis compared to placebo. Alendronate is more effective than alfacalcidol in increasing bone mineral density and reducingvertebral fractures in men with osteoporosis. Alendronate is not superior to alfacalcidol or calcitonin in increasing the bone mineral density in preventing men osteoporosis. Alendronate compared to combination of parathyroid hormone does not show more effectiveness in increasing the bone mineral density in men with osteoporosis. More RCTs of high quality, especially multiple center trials are needed to generate ber evidence.