This handbook contains selected estimation methods for physicochemical properties of organic chemicals. Specific instructions are given for the use of each estimation method. The properties covered include conventional properties off pure materials, properties that describe how a chemical behaves or interacts with a second substance solubility in water, diffusion coefficient in air, interfacial tension with water), and the fate of trace concentrations in specific environmental situations rate of hydrolysis in water, atmospheric residence time, and volatilization from soil). Chapters related to environmental fate propose models that require input information on the environmental compartment of concern as well as chemical-specific properties. The properties of rate of aqueous photolysis and rate of biodegradation are included even though the current state of the art does not permit quantitative estimation. Two chapters stress the importance of photolysis and biodegradation in environmental fate and should allow a qualitative determination of the susceptibility of an organic chemical to these forms of degradation. Additional properties that may be estimated include: critical temperature, critical pressure, Henry's law constant, mass transfer coefficients, molar refractivity, molar volume at the boiling point, and parachor. Twenty-six chapters are processed separately for inclusion in the appropriate data bases.