In view of the high incidence of rickets in infants of women practising purdah (the use of veils) in northern Nigeria we conducted a study on plasma calcium, phosphate, and serum 25-hydroxyvitamin D (25 OHD) concentrations in pregnant Nigerian women and in cord blood obtained from the newborns. Plasma calcium, phosphate, and serum 25 OHD concentrations were lower in practising women and their newborns than those not practising purdah and their infants, respectively. The concentrations of 25 OHD in all Nigerian women were greater than those observed in caucasian women in the United Kingdom. These data emphasise the role of exposure to sunshine in regulating serum 25 OHD concentrations and the adverse effect of deliberate exclusion of sunshine and are consistent with previous data indicating hypovitaminosis D in purdah clad women and their newborns in Saudi Arabia. These data do not, however, provide an explanation for the pathogenesis of the high incidence of neonatal rickets and tetany in infants born of purdah clad women as these women have 25 OHD concentrations greater than those in caucasian women in the United Kingdom.