In 1971 and again in 1977, Costello reported on two unrelated children with multiple congenital malformations associated with growth and developmental retardation and nasal papillomata (Costello, NZ Med J 74:397, 1971; Costello, Aust Paediatr J 13:114-118, 1977). Subsequently, two similar cases were described (Der Kaloustian et al., Am J Med Genet 41:69-73, 1991; Martin and Jones, Am J Med Genet 41:346-349, 1991). Costello syndrome is now a distinct entity. We describe another patient who additionally had hitherto unreported malformations, such as hydrocephalus, seizures, atrial fibrillation, and flutter with atrial septal defect. Although no nasal lesions were found he had laryngeal papillomata associated with a congenital web. A skin biopsy showed no evidence of lipid or mucopolysaccharide storage disease and muscle biopsy was normal by gross and electron microscopic examination.