Besides some beneficial effects of UV exposure, i.e. skin tanning and vitamin D production, UV ex-posure can have deleterious effects on human health. Deleterious effects are a.o. skin cancer, skin aging, wrinkling, cataract, snow blindness, and effects on the immune system. The objectives of this project are especially aimed at the detection of UV effects on the human immune system and as a consequence of the UV induced immunomodulation effects on the resistance to infections and tumors. Research activities Research activities are focussed at laboratory animal studies, studies with human volunteers, epidemiology and mathematical modelling.