PURPOSE OF REVIEW: The aim of this article is to describe recent developments in human studies of the role of vitamin D in the etiology and treatment of cancer. RECENT FINDINGS: Epidemiologic studies over the past year lend additional support for important roles for vitamin D in the natural history of several cancers. Studies showing risk reduction by vitamin D in prostate, colon and breast cancers were joined by new analyses of endometrial, skin, and pancreatic cancers. Interest in vitamin D has extended to examinations of its influence on premalignant conditions such as adenomatous polyps and breast density. Studies of vitamin D and cancer survival have featured prominently in the recent literature. Sun exposure and indicators of high vitamin D status were found to be associated with improved survival for cutaneous melanoma, Hodgkin's lymphoma, and cancers of the lung, breast, prostate and colon. Therapeutic trials of vitamin D are especially prominent in the treatment of prostate cancer. SUMMARY: Studies over the past year indicate potentially important roles for vitamin D in cancer prevention, survival and treatment.