Vitamin D deficiency in immigrants has been known in the UK for 30-40 years. In Denmark, we have become aware of the problem only recently. Of 69 randomly chosen Palestinian women living in Denmark 85% were found to have very low levels of 25-hydroxyvitamin D (< 10 nmol/l). Vitamin D deficiency is caused by inadequate exposure to sunlight and a low dietary content of vitamin D and calcium. Typical symptoms are muscle pain, muscle spasms, diminished muscular strength, deep bone pain, and paraesthesias. The diagnosis can be tested by three blood tests: serum 25-hydroxyvitamin D, serum PTH, and serum alkaline phosphatase. If a combination of low 25-hydroxyvitamin D and secondary hyperparathyroidism is found, the treatment should be high-dose ergocalciferol or cholecalciferol (100,000 IU weekly). If only (isolated) low 25-hydroxyvitamin D is found, treatment with 1000 IU of ergocalciferol or cholecalciferol in combination with one gram of calcium daily will be adequate.