Quality of life is of major concern to patients when choosing a treatment for prostate cancer. Health-related quality of life (HRQOL) is a patient-centered variable from the field of health services research that can be assessed in a valid and reliable manner. Using standardized questionnaires specifically designed to measure HRQOL in men with prostate cancer, we can now study the effect of various treatments on patients' quality of life. Treatments for metastatic prostate cancer can have significant effects in all areas of patients' quality of life. Patients with localized disease undergoing radical prostatectomy (RP) tend to have more sexual and urinary dysfunction than do men undergoing external beam radiation therapy (EBRT), although both groups have worse quality of life in these areas than age-matched controls. Men undergoing EBRT have worse bowel function than age-matched controls or men undergoing RP. Recent studies of men undergoing interstitial brachytherapy indicate that these patients have less urinary leakage than those who undergo RP, but experience considerably more irritative voiding symptoms, which can profoundly affect quality of life. Patients need to be informed of the possible impact of therapy on quality of life when choosing treatment.