The Pallister-Hall syndrome (PHS) was initially described as the congenital hypothalamic 'hamartoblastoma' syndrome in 1980. Cardinal manifestations of the syndrome consist of a hypothalamic hamartoma and extracranial abnormalities, initially thought to be fatal in the perinatal period. The original pathologic description of these hypothalamic lesions were from infants who died in the perinatal period and revealed small cells of variable density which resembled primitive undifferentiated germinal cells and appeared to invade the hypothalamic nuclei, suggesting a neoplastic potential. Hypothalamic lesions have now been removed from older infants and children with this syndrome and reveal a more mature histologic appearance typical of a hypothalamic hamartoma. We present 2 new cases of PHS who underwent surgery and demonstrate the maturational nature of the hypothalamic lesion and the phenotypic variability of the syndrome.