Normal ageing is associated with a decline in lean body mass, muscle mass and strength. The functional consequences of these changes may be significant and include falls, fractures, loss of mobility and increasing dependency. The anabolic actions of testosterone on muscle have been known for over 60 years, and replacement studies in young hypogonadal men have shown that testosterone can improve muscle mass and strength. In addition, the supraphysiological replacement of testosterone in young eugonadal men has also been shown to increase muscle mass and improve strength. Although the data are limited, studies of testosterone replacement in healthy older men with relative testosterone deficiency have demonstrated some modest improvements in muscle mass and strength, although the clinical and functional relevance of the muscle changes have yet to be determined. More data and experience are needed before testosterone can be advocated for the prevention or reversal of sarcopenia in the ageing male.