Fourteen patients with locally recurrent prostate carcinomas after external beam irradiation received 135I seed implants at Stanford between 1975 and 1979. Clinical local control has been obtained in 11 of the 14 patients for follow-up periods of 6 to 36 months. Eight remain without evidence of disease, but 2 of the 3 patients whose pelvic lymph nodes were involved by carcinoma have developed distant metastases. Complications, consisting of either cystoproctitis, urinary incontinence, or the development of a vesicorectal fistula occurred in 4 of the 14 patients. These complications were noted only in those patients who had implantation of high intensity 125I seeds (greater than 0.50 mCi) into large prostatic volumes (greater than or equal to 50 cc). No complications occurred in patients who received lower intensity 125I seed implants in smaller prostatic volumes. We conclude that 125I seed implants may be used in a second attempt to obtain local control after a local relapse following external beam irradiation, if the use of high intensity 125I sources and/or the implantation of large prostate volumes are avoided.