Quality of life is a major concern of patients when they are choosing treatment for prostate cancer. Health-related quality of life is a patient-centered variable from the field of health services research that can be measured in a valid and reliable manner. Using standardized questionnaires specifically developed to capture health-related quality of life data in men with prostate cancer, the effect of treatments on patients' quality of life can be studied. Patients with localized disease who are undergoing radical prostatectomy tend to have more sexual and urinary dysfunction than men undergoing external beam radiation therapy, although both groups have more impairment in these areas than age-matched controls. Men undergoing external beam radiation therapy have worse bowel function and more urinary distress from irritative voiding symptoms than men undergoing radical prostatectomy or age-matched controls. Recent studies of men undergoing interstitial brachytherapy indicate that these patients have less urinary leakage than those who undergo radical prostatectomy, but experience considerably more irritating voiding symptoms, which often profoundly affect their quality of life. Better information regarding the potential impact of prostate cancer treatment on quality of life will improve medical decision-making.