PARIS III is a third generation Windows-based computer software to assist the design of solvents by estimating values of the solvent properties that characterize the static, dynamic, performance, and environmental behavior of the solvent. PARIS III works with single solvents or solvents with multiple components. PARIS III finds either a single chemical or a mixture that matches these estimated values within user-defined tolerances. PARIS III allows the user to search for replacement solvents with higher or lower values of any of these parameters to suit particular applications. Using PARIS III, one could, for example, design a chemical mixture that had an air toxicity index half the value of that in the currently used solvent while keeping other properties approximately constant or even improving them. The static properties considered by PARIS III are molecular mass, molar volume, boiling point, vapor pressure, surface tension, and infinite dilution activity coefficients. The dynamic properties are viscosity and thermal conductivity. The performance requirement is the flash point. The environmental requirements are an air index and an overall environmental impact index. PARIS III screens solvents to ensure the replacements are only in liquid phase.