The thermodynamics of the formation of higher alcohols from synthesis gas was investigated by calculating the equilibrium composition of a system containing CO, H-2, CO2, H2O, and all of the possible isomers of the C1 through C4 alcohols. These calculations were performed using the Gibbs free energy minimization module in the ASPEN PLUS process simulation package. Parametric studies were carried out to define the effects of temperature, total pressure, H2/CO ratio, the presence or absence of the water gas shift reaction, and the recycle of certain alcohol species, based on the assumption that the final system is an ideal gas. Calculations were also done to determine the conditions under which the product can form two or more phases, and whether the formation of multiple phases has a significant effect on reactant conversion or product yield. The effect of fluid-phase nonidealities was also investigated. The calculations showed that the equilibrium conversion of the limiting reactant, either H-2 or CO, is above 90% and that the C4 alcohols are the dominant product at temperatures up to 773 K. Tertiary butanol is the preferred alcohol isomer below about 473 K; isobutyl alcohol is the preferred species between about 473 and 773 K. Multiple product phases are predicted under certain conditions. Some product yields are changed significantly by considering simultaneous chemical and phase equilibrium. Accounting for fluid-phase nonidealities does not significantly change the alcohol product distribution or the reactant conversion, as compared to results based on ideal mixture assumptions.