Findings from a prospective phase II trial in 300 men with ≤cT2b, Gleason score 6 or 7, treatment-naive prostate cancer demonstrate the safety and efficacy of permanent-seed implantation brachytherapy without hormonal therapy. Ten biochemical failures occurred and one patient died of prostate cancer. The median 5-year PSA level was 0.01 ng/ml and 5-year overall survival was 94.9%. Most men (>90%) were “satisfied or extremely satisfied” at 2 years and 4 years after implantation.