Serum and hair zinc concentrations were measured in samples taken from 29 mothers with neural tube defects (NTD) (mainly anencephaly) at delivery. The control group consisted of 20 healthy mothers with normal offspring and 40 nonpregnant women 18 to 34 years of age, from middle income backgrounds. The mean maternal serum and hair zinc concentrations in the NTD group were lower than those of control mothers and the nonpregnant women. The zinc levels in the blood (plasma, red blood cells) and hair of 8 newborn infants with NTD (4 being anencephalic) were compared with those of normal newborn infants. The mean zinc concentration in the hair of malformed babies (250.4 +/- 85.2 micrograms/g) was significantly higher than that of normal infants (193.4 +/- 39.2 micrograms/g) (p less than 0.05) while the mean plasma zinc concentration was significantly lower (59.48 +/- 9.18 micrograms/dl compared with 68.75 +/- 10.89 micrograms/dl) (p less than 0.01). No difference was found between the mean values of red blood cell zinc levels for the two groups of infants. Maternal zinc deficiency was thought to be one of the factors responsible for NTD in Turkey.