In March, 1976, vitamin-D status was investigated in 256 thirteen-year-old school boys of Asian, West Indian, andEuropean origin in Birmingham. Serum-25-hydroxyvitamin-D3 (25-OHD3) concentrations in 78% of the 124 Asian boys resembled those found in rickets and osteomalacia. Serum-25-OHD3 concentrations were also low in a few West Indian and European children. Dietary intake of vitamin D and exposure to sunlight were similar in each group. Serum-parathormone concentrations were increased in many children with low serum-25-OHD3. Reinvestigation in October, 1976, of a group of children whose serum-25-OHD, concentration had been less than 8 microng/l in March, 1976, showed pronounced improvement in all, but some still had concentrations which indicated a possible deficiency. It is suggested that the high frequency of vitamin-D deficiency in Asian adolescents would be much reduced if 1 mg of vitamin D3 was given orally each school term during adolescence.