S-adenosyl-L-methionine (SAM) has proven to be fairly stable in gastric and duodenal juices as well as in bile. It was, therefore, administered orally to six healthy subjects. No increase in SAM levels was observed in the systemic blood. SAM was then directly injected into a jejunal loop of nine patients undergoing cholecystectomy. SAM concentrations increased significantly in venous mesenteric and systemic blood. Infusions of methionine directly into the jejunum by the same method used for SAM did not induce any increase in SAM concentrations in the mesenteric or systemic blood.