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^<13>C NMR spectroscopy was applied to studying lysine biosynthesis in Corynebacterium glutamicum ATCC 21543, a lysine producing mutant. It was cultured in a medium containing [1-^<13>C]glucose or [6-^<13>C]glucose as the sole carbon source and the ^<13>C NMR spectrum of the culture filtrate was measured. ^<13>C labeling patterns of L-lysine produced were well explained by the putative metabolic pathways of the bacterium. Fixation of ^<13>CO_2 liberated from the labeled substrates and the operation of the tricarboxylate cycle in the fermentation were obviously observed. The dual operations of the classical diaminopimelate pathway and the diaminopimelate dehydrogenase bypath were supported. Calculation of the contribution ratios of the metabolic pathways was attempted.