Analysis of 116,699 deliveries (1062 twin pairs and 115,637 singletons) which occurred from 1984 to 1996 at the largest obstetric center in Campinas, SP, Brazil, provided the following conclusions: 1) despite the low percentage of twin births (0.9%), 10.7% of all early neonatal deaths and 3.5% of all stillbirths were twins. Compared to singletons, the likelihood of stillbirths and early neonatal deaths among twins was 1.9 and 6.5 times greater, respectively. 2) The proportion of twins among early neonatal deaths tended to decrease, probably because of improvements in prenatal and perinatal care. 3) The critical period for early neonatal deaths in singletons and twins lasted for the three first days after birth. 4) The incidence of perinatal deaths among twins was highest among MM pairs, followed by FF pairs, and lowest among MF pairs. 5) There was a trend towards a decrease in the annual rate of early neonatal deaths among both singletons and twins, and of stillbirths among singletons, the latter being more conspicuous among females. 6) The sex ratio of singletons was practically stable among living newborns, but showed strong cyclic variation among early neonatal deaths, and a tendency to increase among stillbirths. Twins who died in the first week, as well as living twins showed a strong increase in their sex ratio from 1984 to 1996. 7) The mean gestational age of singletons was highest among living newborns followed by stillbirths, and was lowest among early neonatal deaths. The mean gestational age of living twins was higher than that of early neonatal deaths, but not different from that of stillbirths. 8) The mean birth weight of singletons and twins was highest among living newborns, followed by stillbirths, and lowest among early neonatal deaths. 9) Apgar scores > or = 7 obtained five minutes after birth are inadequate as a reliable indicator of the clinical condition of the newborn, since almost half of the early neonatal deaths had 5-min Apgar scores varying from 7 to 10.