Objective: Vitamin D plays a major role in Ca and bone metabolism, and its extraskeletal functions are being appraised. Although inadequate vitamin D concentrations have been reported in populations worldwide, too little is known about vitamin D status and its determinants among children in developing countries. We aimed to determine vitamin D status and its determinants in Nepalese children of pre-school age. Design: A community-based, cross-sectional study. Setting: Rural Nepal at latitude 27·39°N. Subjects: Healthy children (n 280) aged 12-60 months, selected randomly from the records of a vitamin A supplementation programme. Blood samples were collected using the dried blood spot technique and analysed for serum 25-hydroxyvitamin D (s-25(OH)D) concentration using liquid chromatographytandem mass spectrometry. Ca intake and background variables were assessed with a structured questionnaire. Results: Hypovitaminosis D, defined as s-25(OH)D concentration less than 50 nmol/l, was found in 91·1 % of the children. S-25(OH)D concentration was not related to gender, socio-economic indicators, sun exposure or nutritional status. Currently breast-fed children had higher s-25(OH)D concentrations (36·4 (SD 13·2) nmol/l) than those who were not (28·6 (SD 9·8) nmol/l, P < 0·001). Adjustment for sociodemographic factors did not alter the results. Conclusion: There is widespread vitamin D deficiency among pre-school children in a rural area of Nepal. In our sample, sociodemographic factors did not affect the vitamin D status of children, but prolonged breast-feeding was associated with higher s-25(OH)D concentrations. Further research is required to investigate the health consequences of poor vitamin D status for this population. Low levels of vitamin D are reported in diverse populations around the world (1-3) , with one review suggesting that as many as 14 % of the world's population have levels inadequate for general well-being (4) . Serum concentration of 25-hydroxyvitamin D (s-25(OH)D) is the standard assessment for vitamin D status in the body and s-25(OH)D concentration of 50 nmol/l or more is considered sufficient for optimal bone-related health outcomes by the Institute of Medicine (5) . Studies from Turkey, the Middle East and India have revealed that up to 50 % of children have vitamin D deficiency (6) . A number of determinants that affect s-25(OH)D concentration in children have been identified and include skin pigmentation, prolonged breast-feeding without vitamin D supplementation and low consumption of foods rich in vitamin D (7) . However, little is known about the vitamin D status of Nepalese children.Nepal is a predominantly Hindu nation bordering Tibet and India, located between the latitudes of 26°N and 31°N. Nepalese cultural values do not restrict sun exposure and about 300 d per year are sunny (8) . A few studies that have investigated vitamin D status in special groups in Nepal, such as pregnant women and alcohol-abusing populations, report a wide range of vitamin D deficiency prevalence rat...