Hypoglycemia is a frequent complication of preterm birth and may lead to later CNS damage. The hypoglycemia incidence and the relative risk factors for the affected preterm infants were assessed. We examined 1,500 preterm infants (<37 weeks of gestational age) consecutively admitted between January 1994 and December 1996 at the Department of Pediatrics of Padua University, and screened for hypoglycemia by Dextrostix within the first hour of life. Hypoglycemia was defined as blood glucose levels <40 mg% at Dextrostix. Among study prematures, 35% had hypoglycemia; while the incidence was 9% at levels of Dextrostix <20 mg%. The relative risk for hypoglycemia (odds ratio, OR) was computed assuming a 99% confidence interval (CI). We found 5 risk factors for hypoglycemia: cesarean section (OR 2.24, CI 1.66-3.03), intrauterine malnutrition (SGA) (OR 1.65, CI 1.08-2.53), NICU hospitalization (OR 1.45, CI 1. 09-1.93), gestational age between 30 and 33 weeks (OR 1.93, CI 1. 34-2.78), and twinning (OR 2.49, CI 1.77-3.56). At levels of Dextrostix <20 mg%, 3 more risk factors were found: cardiopulmonary resuscitation at birth (OR 4.06, CI 2.52-6.54), neonatal respiratory distress syndrome (OR 2.21, CI 1.34-3.36) and gestational age between 26 and 29 weeks (OR 2.16, CI 1.02-4.25). The identification of relative risk factors could be useful in improving the hypoglycemia prophylaxis, and in reducing related later CNS abnormalities.