Lyman &agr; measurements of the exosphere of Venus made by the ultraviolet photometer on Mariner 5 on October 19, 1967, are analyzed. Radiative transfer models for a spherical isothermal hydrogen atmosphere with carbon dioxide present as a pure absorber are used to determine the exospheric temperature and density at the bright limb and on the dark disc. It is found that (1) the bright limb data have two components with exospheric temperatures of 275¿¿50¿K and 1020¿¿100¿K and densities 2¿1¿105 cm-3 and 1.3¿103 cm-3, respectively, (2) the dark disc data are best fit by a two-component density model with exospheric temperatures of 150¿¿50¿K and 1500¿¿200¿K and densities 2¿1¿105 cm-3 and 103 cm-3, respectively, and (3) the dark limb exhibits only a hot component because of the very low temperature of the cold component.