A total of 71 men with clinical T1b-T2c carcinoma of the prostate underwent ultrasound-guided interactive seed implantation of the prostate. Sixty received 125I and II 103Pd implants. A laparoscopic lymph node dissection was performed in 58 patients. The patients have been followed a mean of 2 years (1-4.2 years). With use of a prostate specific antigen (PSA) value of 1 ng/ml, patients (n = 8) who presented with an initial PSA of < or = 4.0 ng/ml were all free from failure. This compared with those who presented with an initial PSA of 4.1-10, 10.1-20, and > or = 20 ng/ml, in whom the freedom from failure rates were 52, 32, and 22%, respectively. Patients (n = 49) who presented with an initial PSA of less than or equal to 15 ng/ml had a median PSA of 0.88 ng/ml at last follow-up compared with 2.25 ng/ml for those with an initial PSA of > 15 ng/ml. Prostate biopsies performed 18-24 months after implantation were negative in 82%. The median PSA for those with a negative biopsy was 0.7 ng/ml vs. 4.9 ng/ml for those with a positive biopsy. There were no long-term persistent urinary complaints. Grade 2 radiation proctitis occurred in three (4.2%). No cases of severe radiation proctitis or cystitis occurred. Urinary retention occurred in four patients (5.6%), one of whom required a transurethral resection of the prostate. No patients developed urinary incontinence. Potency was preserved in 94%. We conclude that the real-time ultrasound-guided transperineal seed implantation technique is an effective and safe method of treating prostate cancer. Longer follow-up is needed to substantiate these early encouraging results.