The decline in testosterone with age has been associated with specific physical changes that affect quality of life and life expectancy, although a cause-and-effect relationship is yet to be established. While female menopause is rapid and well described, "male menopause" or androgen decline in older men is gradual and marked by nonspecific symptoms. This makes diagnosis of true testosterone deficiency and prediction of response to testosterone replacement therapy (TRT) challenging. This article reviews androgen decline in men, focusing on those over age 40, and covers symptoms, indications, contraindications,diagnosis, treatments, and the risks and benefits of treatment [corrected].