A user-friendly software package was developed for the compilation and prediction of intemedia transfer factors for air toxics in support of the California Air Resources Board (ARB) multipathway exposure assessment methodology. The intermedia transport factor predictor (ITFP) software consists of three main components. The first is a chemical property database (CHEMBASE) which contains environmentally relevant physicochemical properties, compiled and critically evaluated from various literature sources, for selected air toxics. The second component is a chemical property predictor (CPP) which contains various methods to estimate a selection of physicochemical parameters for different chemical classes. The CPP is based, in part, on chemical-class specific correlation developed specifically for the ITFP software. Finally, the third component is an intermedia transport parameter predictor (ITPP) which is capable of estimating parameters such as dry deposition velocity, wet scavenging coefficients for chemical in the particle-bound and gaseous forms chemical water / air mass transfer coefficients, and half-life for chemical volatilization from the soil. The ITPP includes both literature-based algorithms and new algorithms developed specifically for the ITFP. The ITFP is modular in its construction and it can be expanded to include additional intermedia transport parameters and chemical property estimation modules.