Pure component properties are required for nearly all of the procedures in the API Technical Data Book. This chapter provides a compilation of properties for many hydrocarbon plus selected nonhydrocarbon compounds. The compounds and properties chosen for inclusion here are those deemed most useful in petroleum refining and associated industries. Further information on some hydrocarbons and many nonhydrocarbons may be found in the Design Institute for Physical Properties Research (DIPPR) Data Compilation: Tables of Properties of Pure Compounds (50). The majority of data for the compounds presented here was taken from the following sources (in order of priority).