Cryptorchidism increases the incidence of malignant testicular tumours. The case is described of a normally functioning male patient with a tumour in an undescended testis, in whom a special type of intersexuality was found: the persistent müllerian duct syndrome, one of the types of male pseudohermaphroditism, in which no disturbances of virilisation occur and which is often associated with cryptorchidism and other developmental anomalies.