Vitamin D status of Asian mothers in Cardiff was investigated during early pregnancy and at the time of the birth of their babies, using serum parathyroid hormone (PTH). Median values in Asian (n 32) and Caucasian (n 63) mothers in early pregnancy were 1.56 and 0.81 pmol/l respectively. PTH levels from a separate sample of nineteen Asian and twenty-five Caucasian mothers at the time of birth were 3.0 and 2.20 pmol/l respectively. Altogether twelve Asian and two Caucasian women had elevated PTH. All Asian women who had high PTH values also had a very low serum 25-hydroxycholecalciferol level (250HD). AU samples were taken from women with no significant medical history and normal obstetric history. These findings suggest that subclinical vitamin D deficiency is still a cause for concern in Asian women. More active measures need to be taken to implement current recommendations to improve their vitamin D intake in pregnancy.Parathyroid hormone: Vitamin D: Pregnancy Vitamin D deficiency can occur whenever the demand for the vitamin exceeds supply, as in periods of rapid growth in fetal life, infancy, early childhood and puberty and during pregnancy, lactation and in the elderly. It was the vulnerability of the growing child to rickets that prompted, in the 1940s, fortification of certain foods with vitamin D with or without Ca, and supplements in the form of cod-liver oil being made available free of charge. Tablets which contained vitamins A and D, Ca,(PO,), and KI were provided free for all mothers during pregnancy and for 30 weeks after delivery. Yet in spite of these measures a small number of cases continued to occur among British infants and young children living in poor social conditions where mothers failed to appreciate the need for vitamin supplements, and when household milk containing small amounts of vitamin D was offered as a substitute for human milk or fortified artificial milks (Department of Health and Social Security, 1980). However, since the early 1960s nutritional rickets has been identified mostly, but not exclusively, in immigrant families, mainly Asians. Prevalences of biochemical and clinical rickets in Glasgow's Asian children of 50 and 5 % respectively were reported in the 1960s and 1970s (Ford et al. 1972;Goel et al. 1976). In Birmingham in the mid 1980s, 40 % of 145 Asian toddlers aged 22 months had low serum vitamin D levels (Grindulis et al. 1986). Osteomalacia has been reported also in Asian women of child-bearing age who had lived for some years in Britain (Stamp et al. 1980) including those who were pregnant (Holmes et al. 1973). Brooke et al. (1980) in a study of vitamin D supplements in pregnant Asian women living in London showed a high incidence of vitamin D deficiency during the last trimester; 37% of 126 women had 25-hydroxycholecalciferol(250HD) concentrations below 4 n g / d at 28-32 weeks gestation.