Pelvic lymph node metastases indicate a poor prognosis for patients with clinically localized prostate cancer but the significance of minimal nodal metastases still is debated. We determined the progression and cancer specific survival rates based on the extent of nodal metastases in 511 patients followed for a mean of 8.6 years (range 2.5 to 17.5 years) after bilateral pelvic lymph node dissection and irradiation therapy. The patients were divided into 4 groups based on the extent of nodal metastases: NO--negative nodes (359 patients), N1--a single microscopic positive node (37), N2--multiple microscopic positive nodes (86) and N3--grossly positive or juxtaregional nodes (29). The risks of distant metastases and of dying of prostate cancer were much greater in the 152 patients with positive nodes (N+) than in those with negative nodes (p less than 0.00005). The risk of metastatic disease at 10 years was only 31 +/- 7 per cent for the NO patients compared to 83 +/- 7 per cent for the N+ patients, and the risk of dying of prostate cancer was only 17 +/- 6 per cent at 10 years for the NO group and 57 +/- 11 per cent for the N+ patients. Patients with a single microscopic node (N1) had a pattern of progression and cancer specific mortality rate similar to patients with more extensive nodal metastases and markedly worse than patients with negative nodes. The risk of distant metastases was 80 +/- 15 per cent at 10 years for the N1 group, 84 +/- 11 per cent for the N2 group and 88 +/- 13 per cent for the N3 group, while the risk of dying of prostate cancer at 10 years was 40 +/- 19, 66 +/- 15 and 58 +/- 24 per cent, respectively. The finding of a single pelvic lymph node containing microscopic metastatic disease markedly worsened the prognosis of our patients with prostate cancer. Once prostate cancer is found within the pelvic lymph nodes the patient has systemic disease unlikely to be controlled by pelvic lymph node dissection and radiotherapy.