In human males 6-7 mg of testosterone are secreted by the testes in a circadian rhythm with a nocturnal rise in testosterone followed by a decline during the day. Testosterone is necessary to induce and maintain secondary sexual characteristics, lean muscle mass, bone density and for normal sexual behaviour and cognitive function in men. Replacement therapy has been shown to be beneficial in men with overt hypogonadism. Natural testosterone should be used and not modified molecules. Testosterone is currently available in oral, intramuscular, subcutaneous and transdermal preparations. Recent advances in testosterone replacement therapy include testosterone gels which provide flexibility in dosing and minimal skin irritation resulting in good compliance, and the development of longer acting intramuscular preparations which result in more stable testosterone levels with longer injection intervals. All patients receiving testosterone should be carefully monitored for changes in hematocrit, liver function, lipid parameters and prostate specific antigen (PSA).This article reviews the current experience with the use of various forms of testosterone for the treatment of male hypogonadism.