In recent years, there has been a resurgence of interest in interstitial radiation as a cost‐effective and efficient method of treating organ‐confined prostate cancer. We describe our 7‐ and 8‐year results with transperineal Iodine‐125 and Palladium‐103 implantation. A total of 551 consecutive patients were treated. Of these, 320/551 (58%) received implant alone (Group I), and 231/551 (42%)—considered higher risk patients—were also treated with a modest dose (45 Gy) of external beam irradiation (Group II). The median follow‐up for Group I was 55 months, and for Group II, 60 months. At 7 years, the actuarial freedom from biochemical failure (prostate‐specific antigen (PSA)≤ 1.0 ng/mL) was 80% in Group I patients, and, at 8 years, 65% in Group II patients. Morbidity was minimal if patients had not undergone prior transurethral prostate resections. The results indicate that interstitial radiation is a valid treatment for clinically localized prostate cancer. Semin. Surg. Oncol. 13:438‐443, 1997. © 1997 Wiley‐Liss, Inc.