OBJECTIVE Survival of extremely low birthweight infants with birthweight <1000 g (ELBW) has increased in recent years, parallel to decline in perinatal mortality rate. This study was part of a geographically defined national study on survival, health, development and longterm outcome of ELBW infants in Iceland 1991-95 focusing on infant and maternal health risk factors affecting infant survival. MATERIAL AND METHODS Information was collected from the National Birth Registry on births and survival of ELBW infants weighing 500-999 g born in Iceland 1991-95. Information was obtained from hospital records of all liveborn ELBW infants and their mothers regarding maternal health, pregnancy, birth, diseases in the newborn period, lifespan and causes of death. Information on causes of death was collected from autopsy records of deceased infants. Comparison was made between the deceased ELBW infants and the control infants that survived. RESULTS The study group consisted of 28 infants that died and a control group of 32 infants that survived. Most of the infants died in the first 24 hours after birth (47%). There was no significant difference in birthweight in the two groups nor regarding age of mothers, smoking, alcohol use and medication. Nearly all mothers of deceased infants (97%) had health problems during the pregnancy, compared to 66% mothers in the control group. Mothers of deceased infants had significantly more common infections (p=0.004). Significant difference was found regarding respiratory distress syndrome and intraventricular hemorrhage in infants that died (p=0.001). CONCLUSIONS The results of the study support that short pregnancy, infection during pregnancy and intraventricular hemorrhage were the main risk factors causing death of ELBW infants in the perinatal and neonatal period in 1991-95.