A case of an embryonal carcinoma of the retroperitoneum in a 23-year-old male is reported. His serum, urinary HCG, serum alpha-fetoprotein, and LDH values were high. After combination chemotherapy, when the tumor markers decreased to within normal values, the retroperitoneal tumor was extirpated. Histologically, a small focus in the embryonal carcinoma and cartilage was seen in the fibrous scar tissue. Immunohistochemically, the cancer cells revealed negativity for HCG, alpha-fetoprotein, and the epithelial membrane antigen. However, with the recurrence of the tumor, his HCG and LDH values elevated. The patient died 8 months after the surgical extirpation of his retroperitoneal tumor.