Abstract: Entry of .sup.13 C-enriched acetyl-CoA into the citric acid cycle results in scrambling of .sup.13 C into the various carbon positions of all intermediate pools. The eventual result is that the .sup.13 C resonances of all detectable intermediates or molecules exchanging with those intermediates appear as multiplets due to nearest neighbor spin-spin couplings. Isotopomer analysis of the glutamate .sup.13 C multiplets provides a history of .sup.13 C flow through the cycle pools. Relative substrate utilization and relative anaplerotic flux can be quantitated. A major limitation of the method for in vivo applications is spectral resolution of multi-line resonances required for a complete isotopomer analysis. It is now shown that (.sup.13 C)homonuclear decoupling of the glutamate C3 resonance collapses nine-line C4 and C2 resonances into three line multiplets. These three-line .sup.