A high-performance liquid column chromatographic technique is reported for the analysis of some tryptophan and phenylalanine acid metabolites in the urine. An acidified and NaCl-saturated urine sample is loaded on to a C18-bonded silica microcolumn. After washing the microcolumn with clean and deionized water, the metabolites of interest are selectively extracted by successive elutions with organic solvents of variable polarity. Acids are eluted first and the neutral compounds with the next fraction. Basic compounds and other neutral substances of higher polarities were eliminated during the washing procedure. The chromatography was performed in the straight-phase isocratic elution mode utilizing 5-micrometers silica-gel columns loaded with a triethanolammonium perchlorate--perchloric acid aqueous solution. The separation achieved have permitted the application of the chromatographic technique to the analysis of urinary metabolites with acceptable accuracy.