Five unrelated patients with a previously unrecognized mental retardation malformation syndrome arepresented. Clinical features common to them include moderate mental retardation, postnatal dwarfism, suscepbibility to infection in infancy, and peculiar craniofacial dysmorphia characterized by long palpebral fissures, high-arched and abnormal eyebrows, heavy and long eyelashes, large ears, short nasal septum and/or depressed nasal tip, and cleft palate. Other anomalies are stubby fingers, deformed vertebra and other bone and joint anomalies, and abnormal dermatoglyphics. The absence of familial occurrence and of consanguinity suggests some environmental causation, but the possibility of an autosomal dominant or X-linked mode of inheritance remains. Based upon our five patients and another five of Niikawa et al, we propose this syndrome as a new disease entity.