A global Monte Carlo model of the exosphere of Venus, simulating the normal exospheric processes, as the production of a 'hot' hydrogen component by charge exchange of H+ with H and O, has been computed. The resulting altitude profiles of atomic hydrogen concentration over both the day and night hemispheres are in reasonable agreement with Mariner 5 and Mariner 10 observations of Lyman &agr;, showing that the ionospheric charge exchange reactions are a significant source of 'hot' hydrogen, possibly the dominant source. However, the uncertainties in the available atomic hydrogen data allow for production of a similar amount of nonthermal H by chemical processes involving H2 as suggested by Kumar and Hunten (1974).