Macrocephaly-cutis marmorata telangiectatica congenita (M-CMTC) is a recently described multiple congenital anomaly/mental retardation (MCA/MR) syndrome of unknown cause. This condition is easily recognizable at birth in children with macrocephaly, cutis marmorata, face and/or body segmental overgrowth, toe syndactyly, midface capillary malformation, and hemimegalencephaly. Cutis marmorata may be absent in some cases. Most patients are developmentally delayed. We describe seven new patients, including two with unusual cerebral manifestations and severe outcome. One of two had a complex congenital heart defect (CHD) and died in the neonatal period. Brain magnetic resonance imaging (MRI) showed generalized cortical dysplasia. The other patient had a stroke episode at age 14 years. Cerebral arteriography showed an abnormal vascular pattern. These findings are consistent with the fact that M-CMTC is a generalized vasculopathy. © 2003 Wiley-Liss, Inc.