During a 13-month period, 363 infants were followed up through the first six weeks to determine the effect of perinatal factors (birth weight, gestational age, type of delivery, and pregnancy and neonatal complications) on umbilical cord separation. Also, breast-feedings and umbilical cord care were studied. Except for cesarean section deliveries, study infants were similar to all infants (N = 1474) admitted to the same nursery during the study period. Cord separation occurred from days three to 45, with a mean of 13.9 days. Infants born by cesarean section were found to have an increased interval for cord separation when compared with infants born vaginally (mean +/- SD, 15.9 +/- 5.0 days vs 12.9 +/- 4.2 days). In this study, delays in separation of the umbilical cord beyond 3 weeks of age was not associated with an increased risk of infection.