In a 2-year (1990-92) prospective national investigation, comprising all stillborn and live-born ELBW infants with a birthweight of < or = 1000 g born at 23 completed weeks of gestation or more, we examined the incidence, neonatal mortality, major morbidity and infant survival in relation to level of care and place of residence. A total of 633 ELBW infants were live-born, i.e. 0.26% of all live-born infants, and 298 were stillborn. The average neonatal mortality was 37% and 91% at 23 weeks, 70% at 24 weeks, and 40% at 25 weeks of gestation. Of neonatal survivors, 8% had intraventricular haemorrhage grade 3, 10% retinopathy of prematurity of stage > or = 3, 2% necrotizing enterocolitis, and 28% were oxygen-dependent at a time corresponding to 36 weeks of gestation. In all, 77% were treated with mechanical ventilation, whereas 19% survived without, almost all of them being CPAP treated. Infant mortality among infants born at level III (tertiary centres) was 30%, at level IIa (with full perinatal service) 46% and at level IIb (with basic neonatal service) 55%. Only 1% was born at hospital level I. Regarding the relation to place of residence, the mortality rates among infants residing in the areas served by levels III, IIa and IIb hospitals were 36%, 45% and 41%, respectively. The referral system thus functioned well, but can be improved, and increased perinatal referral, at borderline perinatal viability, might provide a better quality of care and a better chance of survival.