In vitro and in vivo studies provide a body of evidence that adequate protection of the skin against ultraviolet (UV)-induced damage requires photostable broad-spectrum sunscreens with a proper level of UVA protection. UVA alone and UV solar simulated radiation (SSR) induce DNA lesions in keratinocytes and melanocytes as reflected by the comet assay and p53 accumulation. UVA and SSR impair the immune system as shown by significant alteration of Langerhans cells and inhibition of contact hypersensitivity response to chemical allergens and delayed-type hypersensitivity response to recall antigens. Any of these detrimental effects is more efficiently prevented by sunscreens with a higher level of protection in the UVA range. The involvement of UVA (fibroblast alteration, increased metalloproteinase expression) and the pivotal need for well-balanced UVA/UVB sunscreens were further demonstrated using reconstructed three-dimensional skin models.