Accurate staging of prostatic carcinoma requires determination of the status of the regional draining lymph nodes. Pelvic lymphadenectomy is the definitive examination but has certain morbidity and even mortality. Lymphography is safe but may not be sufficiently accurate. A total of 41 patients with clinically localized disease and abnormal or suspicious lymphograms underwent percutaneous lymph node biopsy. Ten of 11 patients (91 per cent) with abnormal lymphograms and 14 of 30 (47 per cent) with suspicious lymphograms had positive cytology studies. Of the suspicious defects an unopacified void in a nodal chain most frequently was positive. Of 22 potentially curable patients with stages A and B1 disease 12 had metastatic disease.