Severe vitamin D deficiency is common among Muslim immigrants. The dose necessary to correct the deficiency and its consequence for bone health are not known for immigrants. The aim was to assess the effect of relatively low dosages of supplemental vitamin D on vitamin D and bone status in Pakistani immigrants. This 1-year-long randomised double-blinded placebo-controlled intervention with vitamin D 3 (10 and 20 mg/d) included girls (10·1 -14·7 years), women (18·1 -52·7 years) and men (17·9 -63·5 years) of Pakistani origin living in Denmark. The main endpoints were serum 25-hydroxyvitamin D (S-25OHD), parathyroid hormone, bone turnover markers and bone mass. The study showed that supplementation with 10 and 20 mg vitamin D 3 per d increased S-25OHD concentrations similarly in vitamin D-deficient Pakistani women (4-fold), and that 10 mg increased S-25OHD concentrations 2-fold and 20 mg 3-fold in Pakistani men. S-25OHD concentrations increased at 6 months and were stable thereafter. Baseline S-25OHD concentrations tended to be lower in girls and women than in men; females achieved about 46 nmol/l and men 55 nmol/l after supplementation. Serum intact parathyroid hormone concentrations decreased at 6 months, but there was no significant effect of the intervention on bone turnover markers and dual-energy X-ray absorptiometry measurements of the whole body and lumbar spine. The large population groups living in a traditional Islamic cultural pattern in Europe are at major risk of vitamin D deficiency due to insufficient sun exposure and low vitamin D intake. Previously, in the cross-sectional part of this study, we found median 25-hydroxyvitamin D (25OHD) concentrations between 10·9 and 20·7 nmol/l among adolescent girls, premenopausal women and men with Pakistani origin living in Denmark (1) . Similar results have been reported in Norway (2 -5) and in the UK (6) . Clinical trials investigating the effect of vitamin D supplementation on fracture risk have shown conflicting results (7 -12) . Several of the trials combined Ca with vitamin D, making it unclear which nutrient is responsible for an observed effect. However, trials with vitamin D supplementation alone (dosages 10 -20 mg/d) also find conflicting results (10,11,13,14) . A meta-analysis of seven randomised trials found that fracture risk was reduced among ambulatory or institutionalised elderly individuals at vitamin D supplemental dosages of 17·5 -20 mg/d, but not at 10 mg/d (15) . However, this differs from a Cochrane review, which found fracture reduction among elderly institutionalised individuals given vitamin D and Ca, but the effect of vitamin D alone was unclear (16) . Bone mineral density (BMD) is a useful measure for predicting fracture risk (17,18) , and BMD was increased with vitamin D and Ca supplementation in some studies among elderly Caucasians (7 -9) and with vitamin D supplementation alone in other studies (19 -21) . Case reports show improvement in vitamin D status (and reduced muscle pain) by vitamin D supplementation among immigrants (...