To investigate possible causes of embryonic and neonatal mortality in a group of captive Fijian iguanas (Brachylophus fasciatus and Brachylophus vitiensis), the vitamin D status of adults in the colony was compared with that of agamid and iguanid lizards either housed in indoor enclosures under artificial ultraviolet light or exposed to natural sunlight (wild-caught or captive animals housed outdoors). Those under artificial lighting had a significantly lower vitamin D status than those housed exclusively outdoors, whereas the vitamin D status of Fijian iguanas that had received intermittent exposure to natural sunlight was intermediate and not significantly different from that of animals housed exclusively outdoors. However, eggs from some of these Fijian iguanas had substantially lower vitamin D content than eggs from outdoor iguanid and agamid animals. Artificial ultraviolet light, therefore, might not be an adequate substitute for natural sunlight to maintain vitamin D status of lizards. This possible inadequacy may be because either artificial ultraviolet light has a lower intensity of the wavelengths that induce vitamin D than does sunlight or the intensity of the artificial lighting is not sufficient.