This paper deals with a three-year-old male patient with sexual precocity due to a gonadotropin-producing hepatoma. Maximum levels of serum-gonadotropins were 340 muULH/ml, 430 muUHCG/ml, but only 1.4 muUFSH/ml. The level of plasma testosterone was 985 ng/dl, and of plasma delta 4-androstenedione 109 ng/dl. Gonadotropin in serum reacted like choriongonadotropin but unlike pituitary luteinizing hormone when compared in dilution tests by radioimmunoassay. Gonadotropin and androgen levels returned to normal after removal of the tumour. Histopathology showed a carcinomatous hepatoblastoma of the epithelial type with immunohistological evidence of beta-HCG production.