Partition coefficients (Kp) in a heterogeneous system consisting of two immiscible organic solvents can be successfully used for a supplementary identification parameter in qualitative GC and GC-MS analysis of organic compounds. For rapid addition to database of Kp values, calculation methods based on the well-known 'retention-structure relationships' approach can be used. This paper reports the experimentally determined and calculated Kp values for 252 compounds including alkyl aromatic hydrocarbons and esters. It is shown that for group identification of components it is desirable to use not the Kp values themselves but the parameter j which is a combination of K, and gas chromatographic retention indices: j = kI - log Kp.