The octanol/water partition coefficients (P-OW) were predicted for five vanadium(IV)-porphyrin complexes which were taken as model compounds of petroporphyrin. The correlation between the reversed-phase liquid chromatographic retention factor and the P-OW observed for standards was applied to the prediction. The log P-OW values estimated for the metalloporphyrins range from 5.8 (for 5,10,15,20-tetramethylporphine complex) to 10.1 (for 2,3,7,8,12,13,17,18-octaethylporphine complex).