Androgen deficiency in the aging male has become a topic of increasing interest and debate throughout the world. The evidence from results showing that testosterone decrease progressively with age and that a significant percentage of men over the age 60 years have serum testosterone levels that are below the lower limits of young adults(age 20~30) men suggest that older hypogonadal men will benefit from testosterone replacement therapy. Long term data on the effects of testosterone replacement therapy in the older population, however, are limited and specific risk data on the prostate and cardiovascular systems are needed. Key questions of functional benefits that may retard frailty of the elderly are not yet available. The recommendations described below were based on document suggested by the International Society of Andrology(ISA), the International Society for the Study of the Aging Male(ISSAM) and the European Association of Urology(EAU) in 2005. The academic committee of the Korean Society for the Aging Male Research(KOSAR) suggested these recommendations to provide the appropriate information about investigation, treatment and monitoring for late-onset hypogonadism in aging Korean men following an annual meeting in October 2006.