Two patients with Moya-Moya syndrome are reported. The first patient has a trisomy 21 and is to our knowledge the third patient reported with the association of Down's syndrome and Moya-Moya. The second patient also demonstrates the typical Moya-Moya picture in angiography. Angiographic follow-up is demonstrated. The presenting age and symptoms, the symptoms in the course of the disease and the prognosis of 120 non-mongoloid cases of Moya-Moya are reviewed.