Group parameters of low-boiling-point compounds (gaseous compounds) for a group-contribution equation of state based on a hole theory previously proposed are newly determined to predict the phase equilibria for gaseous compound + solvent systems at high temperatures and pressures. The gaseous compounds studied in this work are ethane, propane, butane, carbon dioxide and ammonia. The solvents are hydrocarbons, alcohols and water. The characteristic parameters of the solid-state molar volumes and external degree of freedom required for the prediction of phase equilibria have been determined from the critical temperatures and pressures of pure compounds. The group interaction energy parameters have been determined from the experimental data of vapor pressures and phase equilibria. Good calculated results are obtained except for gaseous compound + water systems.