Since the introduction of the nerve-sparing radical retropubic prostatectomy, there has been a steady increase in the number of prostatic cancer cases treated operatively and concern with the frequency of positive resection margins has developed. To identify factors that determine resection margin status the hospital charts of 199 radical retropubic prostatectomy patients from 1980 to 1987 were reviewed, as well as slides from 52 patients in 1987. Of the 199 patients 92 (46%) had positive resection margins; there was no difference in the frequency between the nerve-sparing and standard procedures. The 1987 slide review showed a positive resection margin frequency of 58%. The presence and extent of positive resection margins were directly related to tumor size. The positive resection margin frequency also increased with poorly differentiated carcinoma, capsular penetration and seminal vesicle involvement. Determination of these risk factors identifies patients at greatest risk for positive resection margins.