Between January 1988 and June 1992, 56 patients suffering from malignant testicular tumors underwent nerve-preserving retroperitoneal lymphadenectomy at the University Hospital in Innsbruck. The tumors were staged according to the nomenclature recommended by the Workshop for Staging and Treatment of Testicular Cancer (Lugano 1979). According to this nomenclature 23 patients had stage I and 33 patients stage II. Thirty-nine patients presented with malignant teratoma, 3 with seminoma and 14 with teratoma and seminoma. The patients with stage I tumors were treated after orchiectomy with nerve-preserving retroperitoneal lymphadenectomy according to the dissection fields of Weissbach et al. In cases of nodal involvement in the retroperitoneum (stage IIa and IIb) a retroperitoneal modified lymphadenectomy according to the margins of Colleselli et al was performed. Patients with stage IIc tumors were treated with three cycles of polychemotherapy. Subsequently, the residual tumor was removed and, if possible, a nerve-sparing lymphadenectomy was performed. Since the nerve-preserving technique was modified in accordance with the tumor stage, antegrade ejaculation could be preserved in 47 of the 56 patients. In 22 patients exocrine testicular function was assessed by sperm analysis. The findings for the patients with stage I and IIa were considerable. The patients who had undergone induction chemotherapy for stage IIb and IIc had poor exocrine testicular function. The follow-up time was 29 months. At follow-up none of the patients presented with recurrent retroperitoneal tumor. Only one patient was found to have tumor progression (solitary pulmonary metastasis 1.7%). These results show that nerve-preserving retroperitoneal lymphadenectomy is the treatment of choice in stage I non-seminomatous testicular tumors.(ABSTRACT TRUNCATED AT 250 WORDS)