Of 368 patients with unilateral testicular cancer, 12 (3.3%) suffered from a second malignant germ cell tumor; five tumors occurred synchronously, seven were treated by bilateral orchiectomy, five were treated by unilateral organ sparing surgery with enucleation of the germ cell tumor in a pilot study. Enucleation was performed for four seminomas and one embryonal carcinoma; an associated carcinoma was found in situ in three cases. The average follow-up time for patients treated conservatively is 22 months; no local recurrence has been detected. Testosterone synthesis is sufficient to obtain normal serum androgen levels. Organ sparing surgery for testicular cancer is possible if the following prerequisites are met: pT 1-tumor, no infiltration of the rete testis, biopsies of the tumor bed are negative, biopsies from peripheral parenchyma are taken and any associated carcinoma in situ is irradiated with 20 Gy.