INTRODUCTION . . . . . ~ the past: traditiOn~ routi~e analys.ls o~ fatt~ acIds Involved elth~r labon~us acld-ba.se titratiOns.I~ .n°n.- aqueous medIa or tedIous extraction and denvitIzation prior to analysis by gas chromatography. It is now possib . to analyze for selected fatty acIds (saturated CIO-CI8 mono carboxylic acids) without derivitization via Ion Chroma- tography using the MPICfM mode. The method of separa tion is based on the degree of absorption of the fatty acids on the neutral, hydrophobic resin. Elution order is deter- mined by hydrophobicity with the shorter chain, more hydrophilic fatty acids eluting first. The separation is controlled by both organic modifier (isopropyl alcohol) and ammonium hydroxide concentration in the eluent. Conductivity detection allows detection of underivitized fatty acids at the low ppm level.