The photoprotection against UVB, UVA and blue light provided by a widely prescribed sunscreen (RoC 15+ A+B) was compared with two new products containing microfine titanium dioxide (Sun E45 lotion SPF 15 and Sun E45 cream SPF 25) [corrected]. Comparisons were made in vivo using photosensitive patients with either chronic actinic dermatitis or erythropoietic protoporphyria, and in vitro using a newly developed spectrophotometric assay. Good agreement was obtained between the in-vivo and in-vitro methods at each waveband. All products showed high protection against UVB radiation, but the products containing microfine titanium dioxide showed significantly higher protection against both UVA and blue light than RoC 15+ A+B. Products containing microfine titanium dioxide are likely to offer superior photoprotection in those patients who are abnormally sensitive to long wavelength ultraviolet radiation than products which are currently available on prescription.