Psychrometric charts for condensing water vapour in Martian atmosphere at four different pressures are presented. The charts are based upon semi- theoretical equations and make use of published physical property data and correlations. The behaviour of the vapour phase is characterised by the Virial Equation of State truncated at the third term. The solubility of gas in water is also considered. The charts are constructed with the dry bulb temperature and absolute humidity scales as the orthogonal axes. Curves of constant adiabatic saturation temperature, constant relative humidity, constant gas specific volume and constant enthalpy deviation are plotted on the charts. (c) 2005 Elsevier Ltd. All rights reserved.