Representative results of the numerical simulation of responses (viz. photocurrent and optimum power output as well as efficiency) of the conventional and violet Si cells and of the Ga1-xAlxAsGaAs and GaAs cells are presented as a function of the solar zenith angle for seven different models of the terrestrial atmosphere. The atmospheric models used vary from an aerosol-free and cloud-free model with gaseous absorption to several models with moderately thick stratus cloud layer and high concentrations of aerosols. This study, restricted to horizontally situated solar cells, illustrates the manner in which characteristics are significantly affected by position of the sun, turbidity and cloudiness of the atmosphere, as well as reflectivity of the underlying surface. © 1976.