As part of a world-wide survey of middle distillate fuel instability, three fuels were chosen for detailed GCIMS analysis. These fuels are identified by number and country of origin; FL-2577 was from Burnaby, British Columbia, Canada; FL-2599 was from Abamadj, Kuwait; and FL 2592 was from Chiba, Japan. The organonitrogen compounds in the three fuels were separated by mild acid extraction followed by silica gel absorption. This treatment yielded three fractions for each fuel; a basic nitrogen compounds fraction, BNC; a non-basic nitrogen compounds fraction in methylene chloride, mcl, NBNC-mcl; and a non-basic nitrogen compounds fraction in methanol, meoh, NBNC-meoh. The three fractions from each fuel were analyzed by combined capillary gclms. The organo-nitrogen compounds from each fraction were identified and quantitated.