The detection rate of adenocarcinoma of the prostate has been significantly increased through introduction of systematic transrectal ultrasound-guided ''mapping'' biopsies of the prostate. In a study of 51 patients, we investigated the histological results of this preoperatively feasible method and compared these with tumor spread and margin positivity in the histological specimen obtained from radical prostatectomy. In a separate study we investigated the morbidity and patient acceptance of the transrectal ultrasound-guided ''mapping'' biopsy in 76 patients. A significant difference between the number of positive biopsies in correlation to the pT-stage was found (pT2: 1.64+/-1.0 versus pT3: 3.08+/-1.6, p < 0.01). Furthermore, a difference between the number of positive biopsies in correlation to positive and negative surgical margins, was seen (3,75 +/- 1,85 vs 1,74 +/- 1,01, p < 0,001). Concerning the prediction of tumor spread in both lobes of the prostate gland, a notable ''understaging'' by ''mapping'' biopsies was found. Morbidity after ''mapping'' biopsy was acceptable. Besides improvement in detection rate, the ''mapping'' biopsy can render important information about tumor extent and the chance of positive surgical margins after radical prostatectomy.