The use of the computer program SOLGASMIX-PV for calculating equilibrium compositions is described. The program can calculate equilibria in systems containing a gaseous phase, condensed phase solutions, and condensed phases of invariant or variable stoichiometry. Either a constant total gas volume or a constant total pressure can be assumed. Unit activities for condensed phases and ideality for solutions are assumed, although nonideal systems can be handled provided activity coefficient relationships are available.