Background: Although sun protection is advocated for skin cancer prevention, sunlight is also important in generation of vitamin D in the skin. There is concern that sun protection may result in an abnormally low level of vitamin D. Objective: To assess the risk of vitamin D deficiency in a sunlight-deprived population, we studied eight ambulatory patients with xeroderma pigmentosum (XP) who practiced intensive sun protection during a chemoprevention study of oral isotretinoin. Methods: We surveyed the patients to determine the extent of sun protection and vitamin D intake and measured the serum levels of two vitamin D metabolites (25-hydroxyvitamin D [25-OHD] and 1,25-dihydroxyvitamin D [1,25-(OH)₂D]), calcium, and parathyroid hormone during 6 years. Results: The patients all wore protective clothing and sunscreens when outdoors. Estimated mean vitamin D intake was normal. The mean values of serum 25-OHD were low normal, but 1,25-(OH)₂D, calcium, ionized calcium and parathyroid hormone levels were normal. Lack of seasonal variation in serum 25-OHD indicated rigorous photoprotection. Conclusion: Despite rigorous sun protection normal vitamin D levels can be maintained in ambulatory patients with XP.