Teratoma contains elements derived from all three embryonic germ layers and mature teratomas are entirely composed of mature differentiated tissues, while immature types always contain additional embryonic tissues of variable degree of immaturity, especially neuroepithelial elements. Twenty cases of teratoma in infancy and childhood were reviewed and the clinical features and pathologic findings including PCNA expression were studied. Sacrococcygeal teratomas were the most common type(45%), followed by retroperitoneal and ovarian teratomas. There was. a predilection of females in a ratio of 4:1 and age distribution was most prevalent below the first year of age(45%). But in ovarian teratomas, the age at diagnosis was above 4 years of age in all cases. Serum alpha-fetoprotein levels were checked in 18 cases. In all mature teratomas and 1 of 5 immature teratomas, the levels were normal. But in 4 of 5 immature teratomas, the serum levels were elevated and progressively declined to normal range after mass excision.