A case of intratubular germ cell neoplasia adjacent to an immature teratoma is described in an 8-month-old boy with normally descended testes. The pattern of intratubular germ cell neoplasia in the infantile testis appeared different from that in the adult, but the abnormal germ cells were morphologically and immunohistochemically similar. In the few previous reports, which have investigated infantile testicular tissue for the presence of intratubular germ cell neoplasia adjacent to germ cell tumours, intratubular germ cell neoplasia in conjunction with a yolk sac tumour and mature teratoma have not been found, and cases with immature teratoma have not been reported. The presence of intratubular germ cell neoplasia in conjunction with immature teratoma and its apparent absence in conjunction with the mature form and with yolk sac tumour may indicate difference in tumour development. Whether there is a true difference in the occurrence of intratubular germ cell neoplasia in the infantile testis according to the various types of germ cell tumours remains, however, to be proven by investigations of more cases.