It is generally believed that among twin pregnancies with one fetal loss prior to delivery, the surviving twin has an increased rate of perinatal mortality and childhood morbidity (cerebral palsy and mental retardation). By using data from the National Medical Birth Registry of Sweden between 1973 and 1983, we identified 206 gestations with the death of at least one twin (in 36 pregnancies both twins died) prior to delivery. The original medical records were retrieved for study. The presence of childhood morbidity for 65 of 129 surviving (8 years of age or older) twins born between 1973 and 1980 was evaluated by a questionnaire sent to rehabilitation centers for disabled children, as well as to offices for the Provision of Care for the Mentally Retarded. Perinatal mortality for a twin after the antenatal death of the co-twin was considerable. Fifty percent of survivors died before 34 weeks' gestation, and 18.7% thereafter. At follow-up, 8 years or more after birth, three twins (4.6%) were handicapped. Our results indicate the need for careful monitoring of the surviving twin fetus after one twin has succumbed prenatally.