The characteristics of solar UVB- and UVA radiation fluxes and global radiation in high mountain areas are evaluated based on measurements taken over years at Jungfraujoch (3576 m a.s.l., Switzerland) and in Innsbruck (577 m a.s.l., Austria). The share of the UVB radiation flux in global radiation shows a marked annual variation, with a maximum occurring in summer which is more pronounced in the high mountains than in the valley. The share of the UVA radiation flux in global radiation, however, is approximately constant over the year with values between 4% and 6% at both altitudes. Further factors excerting a considerable influence on solar UV radiation fluxes are cloudiness and albedo. Cloudiness affects the UVB- and UVA radiation fluxes less than it does global radiation. Over dry new snow, the albedo is higher for UVB radiation than for global radiation, but smaller over snow-free terrain. The altitude effect of UVB- and UVA radiation fluxes and of global radiation depends on the season and is greatest for the UVB radiation flux. Using Green’s radiation model, the altitude effect was determined for broad-band UVB- and UVA ranges as a function of albedo and turbidity and was found to correspond well with the measured values. To evaluate biological effective doses, the maximal daily totals for erythema, immediate and delayed tanning in the seasonal course were calculated and discussed in connection with the protective action of pigmentation. The keratitis effective irradiance was calculated for a situation in which the eye is directed to horizontal surfaces. In the Alpine area, keratitis generally occurs only in snow-covered terrain from about mid-February onwards. For the period from 1981 to 1989 an annual increase in the solar UVB radiation flux of 1.1 ± 0.4% was measured at Jungfraujoch, which is related to a decrease in total ozone of 0.23% per year, measured in Arosa (Switzerland).