OBJECTIVE In relapsing testicular cancer, additional chemotherapy is followed by abdominal CT. If residual lesions are found, retroperitoneal lymphadenectomy is considered. We studied retrospectively whether morphological criteria can help in selected cases in deciding about lymphadenectomy by distinguishing between vital tumor, scarring and mature teratoma. METHODS In 26 patients who had been treated by salvage chemotherapy and retroperitoneal lymphadenectomy for non-seminomatous testicular cancer between 1990 and 1997, abdominal computed tomography and histology were correlated. RESULTS Histological examination found scarring in 10 patients, vital tumor in 6, mature teratoma in 4, and simultaneous teratoma and vital tumor in 6. A single CT criterion for distinguishing between these histologies was not identified. In two patients with large masses which were partly cystic and partly solid vital tumor and teratoma were verified. Scarrings may be expected in cystic lesions at the level of the renal hilus which are lined by a thin and smooth wall. Size did not matter. CONCLUSIONS Accurate differentiation between vital tumor and necrosis was not possible. Before lymphadenectomy CT, however, localised lesions.