Transrectal microwave hyperthermia was applied to 46 stages D1 and D2 prostate cancer patients to treat urinary symptoms and local pain unrelieved by total androgen ablation therapy. Hyperthermia was administered in 10, 60-minute sessions twice a week for 5 weeks. A calculated intraprostatic temperature of 43.5 +/- 0.5C was maintained throughout the treatment. At 2 years the mean residual urine volume was significantly decreased (p less than 0.05), while the mean peak flow rate and maximum flow nomogram were improved but not significantly. The majority of patients reported a notable amelioration of subjective symptoms and quality of life. The only complication was a prostatorectal fistula that was cured by leaving a urethral catheter in place for 4 weeks. Prostatic hyperthermia is a safe and effective palliative procedure for bladder outlet obstruction due to advanced prostate cancer.