In order to find the optimum conditions for gas chromatographic separation of chlordimeform, demethyl ohlordimeform, N-formyl-4-chloro-0-toluidine and 4-chloro-O-tolnidine in urine, five columns were tested. The best separation of these four compounds were obtained with 1% PVP and 8% 20 M on 80~100 meshes white diatomeous support No. 101 (acid and base washed).Using O-diallyl phthalate as the internal standard, this column can be used both for qualitative and quantitative analysis of these four compounds. Another metabolites, 5-chloroanthranilic acid may be estimated on the same column after conversion to its methyl ester.