Chromatographic behavior of nitrogen compounds differed from others.The column efficiency was poor for the compounds and sometimes solutes were not eluted out from a column. Therefore, the elution volume of alkylamines, anilines, pyridines, pyrazines, quinolines and aminopolyaromatic hydrocarbons was measured on a methacrylate gel and octadecyl bonded silica gels in pH controlled acetonitrile/water mixtures.The solvent effect on the dissociation constant differs from that obtained for aromatic acids.The values in acetonitrile/water mixtures are smaller than those obtained in 1 0 0 % water.The linear relation between log P and log k' values is obtained in eluents of pH 7 where the retention of these compounds is maximized. Some hydrophobic fragmental constants are proposed from this result.Prediction of retention time of these compounds from their log P values can be done in the individual groups on octadecyl bonded silica gels in pH controlled acetonitrile/water mixtures.