A case of metastatic spermatocytic seminoma with metastases to homolateral retroperitoneal paraaortic lymph nodes in a 50-year-old man is described. The metastases were detected 18 months after orchiectomy. A retroperitoneal biopsy with cytoreductive lymphadenectomy was performed followed by radiotherapy and consecutively by combination chemotherapy. The patient died 25 months after orchiectomy of complications arising after a second course of chemotherapy. No signs of further tumor spread were observed. Autopsy was not performed. The tissue of the metastases fulfilled the light microscopic criteria for spermatocytic seminoma and ultrastructurally showed intercellular communications with typical intercellular bridges. The absence of placental alkaline phosphatase in tumor cells is also consistent with this diagnosis. The metastases differed from the primary tumor in the presence of focal lymphocytic infiltration and granulomatous reaction. This patient represents the first fully documented case of a metastasizing spermatocytic seminoma.