Most of the population receive their nutritional vitamin D requirements through exposure to solar ultraviolet (UV) radiation, with cutaneous synthesis estimated to provide 80-100% of the vitamin D requirements of the body. However, little is understood about the basic interaction of sunlight (UV) exposure and the subsequent photobiology and photochemistry of vitamin D production in humans. Low vitamin D (blood serum 25[OH]D) status has been linked to the development of a surprisingly wide range of diseases. Epidemiological data and animal studies indicate that low vitamin D is linked to rickets, bone mass loss, multiple sclerosis, hypertension, breast cancer, prostate cancer, colorectal cancer, insulin dependent diabetes and schizophrenia. Importantly some this emerging research associates such diseases with location and subsequent ultraviolet radiation exposures. This paper overviews concepts important to consider when assessing the impact of location and UV exposure on vitamin D synthesis.