A well-trained young male developed effort-induced dyspnea due to marked lactic acidosis. In the absence of cardiopulmonary problems, enzyme defects, primary hepatopathy or myopathy, abdominal angiography revealed subtotal stenosis, and duplex sonography (15 years later) total occlusion, of the celiac trunk associated with hepatic steal syndrome. We suggest that the marked, effort-induced lactic acidosis may be a metabolic consequence of Dunbar syndrome (stenosis of the celiac trunk due to compression by the crura diaphragmatica).