Forty-two patients with carcinoma of the prostate have been studied by bipedal lymphangiography, abdominal CT scanning and percutaneous transabdominal lymph node aspiration cytology to try to increase the accuracy of lymph node staging. The use of two independent radiologists to report the lymphangiograms did not improve the accuracy of reporting. CT scanning was of value only in patients in whom the lymph nodes were not opacified on lymphangiography. Aspiration cytology was positive in 8 of the 40 patients who were studied. There was no morbidity. Six of these 8 patients had MO disease, three had TO tumours and were not on treatment. A poor correlation was found between the presence of lymph node metastases and the Gleason score. Percutaneous transabdominal lymph node aspiration cytology is a safe procedure. When positive, it avoids the need for a staging lymphadenectomy and so helps to identify those patients for whom local treatment is not applicable.