: Although many theories relating the pineal secretory product melatonin to aging have been put forward, the role of this agent in the aging process is not clear. However, there are several reasons to postulate a role for melatonin in this process. Melatonin levels fall gradually over the life-span. Melatonin is a potent free radical scavenger. Melatonin deficiency is related to suppressed immunocompetence. In at least one animal model melatonin supplementation increased life-span although several other studies have failed. The aging process is multifactorial, and no single element seems to be of basic importance. It seems, however, that although melatonin can not be univocally recognized as a substance delaying aging, some of its actions may be beneficial for the process of aging. However, the precise role of melatonin in the aging process remains to be determined.