A boy with complete triploidy and extensive external and internal congenital malformations who survived for almost seven months is presented. He was born after 31 weeks of gestation, was utterly small for gestational age and the delivery was induced because of intrauterine asphyxia. The infant had typical features of the complete triploidy syndrome. He did not develop mentally or motorically even to a normal neonatal level. Banding analysis of chromosomes and HLA-antigen typing of the patient and his parents suggested that the abnormal cell division had occurred during the oogenesis. The boy suffered a fatal Pneumocystis carinii infection, suggesting defective cellular immunity. In the vast majority of previously reported cases of complete triploidy the infant has died either before birth or within the first postnatal hours and except for four patients, all reported patients have died before the age of 2 months. Our patient illustrates the fact that with modern neonatal intensive care, infants with severe malformation syndromes can survive for longer periods than previously, but in the case of patients with the complete triploidy syndrome without developing mentally at all. The ethical problem of artificially prolonged survival in severely handicapped children is discussed.