The recognition of andropause, the middle-age stage in male development comparable to women's menopause, is hampered by the lack of a clear outward manifestation of the chemistry and physiology specific to aging men. Men are still capable of reproduction well into and beyond middle age. Yet a man's sexual desire and potency varies, often according to his testosterone level. Recent studies show that the lowered testosterone levels endemic in aging men are being exacerbated by environmental agents. Testosterone-blocking estrogen agents are present in insecticides, industrial materials, pharmaceuticals, and foods. Men are daily inundated with a "cocktail" of estrogen agents that alter the fine balance of testosterone that makes them male.