Abstract: In accordance with a method and an apparatus for determining an individual's ability to stand exposure to ultraviolet radiation prior to causing a skin reaction, such as skin cancer or erythema, or for determining an individual's ability to become tanned by exposure to ultraviolet radiation, at least part of the individual's skin surface is exposed to electromagnetic radiation of a predetermined spectral composition, e.g. visible light, and of a predetermined intensity. The intensity of electromagnetic radiation reflected from the part of the individual's skin surface is measured so as to determine the coefficient of reflection of the part exposed to electromagnetic radiation of the predetermined spectral composition.