Benign prostatic hyperplasia (BPH) is a very common condition in older men, affecting up to 80% of men aged >or= 80 years in the United States. It typically leads to lower urinary tract symptoms, which often require medical management. The exact cause of BPH is unknown, and the only 2 established factors associated with BPH are age and the presence of androgens. Although the presence of testosterone is required for the development of BPH, testosterone is not thought to be the underlying factor causing BPH because testosterone levels decrease in older men. Recent studies have reported that BPH is associated with elevations in plasma estradiol/testosterone ratio, insulin, and insulin-like growth factor-I. Daily aerobic exercise can reduce all of these plasma factors, particularly when combined with a low-fat, high-fiber diet consisting of whole grains, fruits, and vegetables. In cell culture studies, this type of lifestyle regimen has recently been shown to reduce the growth of serum-stimulated prostate epithelial cells and the growth of androgen-dependent prostate cancer cell lines.