After a description of the important observational facts for Mars, a discussion is given of the probable vertical structure of the Martian atmosphere based upon the ideas of radiative equilibrium in the stratosphere and near convective equilibrium in the troposphere. The proposed tropopause temperature is low enough to cause condensation of CO2 and thus may explain the blue clouds of Mars. Radiometric observations of temperatures on Mars are used to delineate the surface temperature field, and this is combined with cloud drift observations to define the circulation pattern. Considerable resemblance to terrestrial circulation is found, but differences exist and are discussed.