Nine patients underwent retroperitoneal nerve-sparing lymph node dissection for bilateral nonseminomatous testicular tumours (path. St. I disease). While the isolated lumbar nerves L1, L2, L3 were electrostimulated (30 Hz, 5-20 V), the activity of these seminal vesicles, bladder neck and posterior urethra was recorded by way of suprapubic transvesical sonography and/or endoscopy. Emission started simultaneously on three different levels: contraction of the seminal vesicles in the periphery, bladder neck closure, and opening of the paracollicular space. Contraction of the seminal vesicles extends to the midline; the prostatic urethra closes, starting at the bladder neck. Secretion from the ductuli prostatici (milky) and from the ductucli ejaculatorii (transparent) follow. It was confirmed by the detection of PSA (11,000-21,000 ng/ml) in the ejaculate that prostatic secretion is also present in it. The significance of the postganglionic nerves for emission increased from L1 to L3. In three patients with salvage lymph node dissection the above-mentioned ultrasound monitoring allowed differentiate nerves relevant to emission from those not involved, allowing more comprehensive retroperitoneal resection.