We report 2 patients with hypothalamic hamartoma associated with multiple congenital abnormalities and analyze 42 (including our own) reported cases, including our 2 cases, of hypothalamic hamartoma or hypothalamic hamartoblastoma with multiple congenital abnormalities, to understand the timing of their occurrence and clarify the prognosis. To this end, we classified them into lethal and nonlethal cases. We found poly- and syndactyly, cleft or high-arched palate and nose abnormalities to be important manifestations of this syndrome. Major organ abnormalities and CNS and endocrine abnormalities occurred frequently among the lethal cases, very likely indicative of a disturbance of embryogenesis between gestational days 34-37 and thus implicated in a negative prognosis.