118 Patients with non-seminomatous testicular cancer (NSTC) in clinical stage I (CSI = no metastases by clinical, radiological and biochemical evaluation) underwent retroperitoneal lymph node dissection (RLND). The operation was done unilaterally (95 patients) in peroperatively tumor-free patients or in those with limited metastatic growth. In 23 patients with more extensive metastases, bilateral RLND was performed. Metastatic lymph nodes were found in 36 patients, and these patients received 3-4 cycles of a cisplatin-based combination chemotherapy. If no metastases were detected the patients had no further treatment. The 5-year disease-free survival rate was 100%. 8 of 82 patients without detected metastases in the operation specimen relapsed (all outside the retroperitoneal space), but were cured by salvage chemotherapy. Solitary metastases were found in 11 patients, whereas 25 patients had more than 1 metastatic lymph node. The size of the largest metastasis ranged from 0.3 to 40 mm. Metastases from right-sided tumors were detected at all levels of the lumbar region, predominantly to the right of the inferior vena cava and/or within the interaortocaval space. Left-sided tumors metastasized to the upper two thirds of the lumbar space, only rarely crossing the midline. This anatomical distribution of metastatic lymph nodes indicates that the presacral sympathetic nerve plexus and the sympathetic nerve fibers around the aortic bifurcation can be spared from extensive resection in the majority of patients with NSTC in CSI. Unilateral RLND or other nerve-sparing techniques are thus possible, preserving antegrade ejaculation in greater than 80% of the patients. This RLND represents a reasonable alternative to the 'surveillance' policy in NSTC.