The metabolism of fumarate by Helicobacter pylori was investigated employing one- and two-dimensional 1H and 13C nuclear magnetic resonance spectroscopy. Metabolically competent cells generated malate and succinate from fumarate as the sole substrate indicating the presence of fumarase and fumarate reductase activities in the bacterium. In incubations of fumarate with cell lysates accumulation of lactate, acetate, formate and alanine was observed after the initial production of malate and succinate. The results indicate the existence of active fumarate catabolism in H. pylori and suggest the possibility of an ATP generating mechanism which may play an important role in the bioenergetics of the bacterium.