‐The analysis of solar erythema dose under changing ozone amount, previously confined to the study of horizontal surfaces, is extended to include the effects of receiver orientation. A semi‐empirical model is used to calculate erythema (sunburn) dose for non‐horizontal plane areas under cloudless conditions as a function of latitude, season, and ozone amount. According to the model, in middle and high latitudes, surfaces with inclination angles (α) up to 45° receive at least 80% of the daily erythema dose received by a horizontal surface. Much larger reductions in daily erythema dose occur for α > 45°. which can result in a significant reduction in the latitudinal gradient of erythema dose. The amplification factor for erythema dose (Δdose/ΔO3) varies significantly with latitude, but it is only weakly dependent upon receiver orientation. Additional calculations indicate that the amplification factor may be significantly larger for skin cancer than for erythema. Copyright © 1979, Wiley Blackwell. All rights reserved