The aim of this study was to determine the incidence of neural tube defects (NTDs) in Izmir, Turkey, and to evaluate risk factors that may be associated with NTD-affected pregnancies. A nested case-control study was carried out in all hospitals in Izmir. Controls were matched with cases on an individual basis according to the newborn's age and hospital in which they were born. There were 56 newborns with NTD out of 36,331 deliveries in Izmir hospitals in 2000. The incidence of NTD was 1.5 per 1000 births. Forty-four cases and 88 controls were analyzed for risk factors. According to chi-square analysis, maternal education, paternal education, maternal nutritional status, maternal drug usage, and presence of maternal chronic diseases and acute infections during pregnancy were found significantly different between case and control groups.