Serum levels of the circulating form of vitamin D, 25-hydroxyvitamin D, and calcium were measured in 104 Saudis, 44 Jordanians, 17 Egyptians and 10 other subjects aged between 18 and 23 years. All subjects were male university students living in Riyadh for more than 2 years. 25-Hydroxyvitamin D levels were (mean ± SD) 12.8 ± 6.3, 11.0 ± 5.8, 11.9 ± 6.9 and 11.9 ± 5.0 ng/ml, respectively. The percentages of subjects with serum 25-hydroxyvitamin D levels below 10 ng/ml were 35, 45, 53 and 50% for normal Saudis, Jordanians, Egyptians and others, respectively. All subjects had normal serum calcium concentrations. There was no correlation between 25-hydroxyvitamin D and serum calcium levels in the subjects investigated. This study indicates a tendency for a low vitamin D status among residents of Saudi Arabia, in spite of abundant sunlight all the year r