This communication brings the number of recognized cases of the C (trigonocephaly) syndrome to 11. The pattern of findings includes an anomaly of the anterior cranium and frontal cortex (trigonocephaly), the root of the nose (broad nasal bridge, epicanthus, and short nose), and palate (thick anterior alveolar ridges); abnormalities of the limbs (polysyndactyly, bridged palmar creases, short limbs, and joint dislocations and/or contractures); visceral defects (congenital heart defects, cryptorchidism, and abnormal lobulations of the lungs and kidneys). Auricular, mandibular, skin, and genital abnormalities also occur. Consistent neurological findings are hypotonia, strabismus, and psychomotor retardation; seizures have been reported. Normal chromosomes, normal parents with multiple affected offspring, equal sex ratio of affected individuals, and consanguineous matings all support autosomal recessive inheritance of the C syndrome. In autopsied cases, there has been a suggestion of defective central nervous system myelination. About 1/2 of the case have died within the first year. All survivors have severe to profound mental retardation except for one child who has moderate retardation.