In order to assess the current nutrition status of Mongolian population, including rickets and vitamin D deficiency of children and women, the Fourth National Nutrition Cross-Sectional Survey was conducted in 21 aimags (provinces) of 4 economic regions of the country and capital city Ulaanbaatar in 2010. Children of age under five years, and non-pregnant women of reproductive age were used as subjects for assessing rickets and vitamin D deficiency. A total of 400 households were randomly selected from each of 4 economic regions and Ulaanbaatar city. Clinical examinations were performed on 706 children of age under five years. Interviews were used to assess vitamin D supplement use. The serum level of 25-hydroxyvitamin D was measured in 524 children aged 6-59 months and in 867 women of reproductive age. This survey found that 21.8% of children had vitamin D deficiency, 20.6% had low vitamin D reserve, and 30.0% of women had vitamin D deficiency and 22.2% had low vitamin D reserve. The prevalence of vitamin D deficiency in children (35.0%, 95% CI, 24.7-47.0) and women (54.9%, 95% CI 45.5-64.0) in the Eastern Region was (35.0%, 95% CI, 24.7-47.0) significantly higher than in the Western, Khangai, Central Regions, and Ulaanbaatar. Further it was found that 27.4% of children under-two years had received vitamin D supplementation. The proportion of children, who did not receive vitamin D supplementation had a higher prevalence of vitamin D deficiency than that of the children of the Eastern Region. None of the women who were involved in this survey had received vitamin D supplementation; 10.2% of them had delivered in the past 12 months, and 22.5% were breastfeeding. The prevalence of classic signs and symptoms of rickets were commonly reported among children of age under five, and skeletal abnormalities more commonly reported in children aged 12-47 months. In conclusion, there is a high prevalence of classic signs and symptoms of rickets in children of age under five years. Vitamin D supplementation in adequate doses for the prevention and treatment of rickets in children is insufficient. Thus, a trial survey is needed to assess the safe and effective doses of vitamin D supplementation necessary for the maintenance of normal serum 25-hydroxyvitamin D concentrations in Mongolian children, and women. In addition, a vitamin D food fortification program is required. This article is part of a Special Issue entitled 'Vitamin D Workshop'.