2-[(2-Pyridylmethyl)sulfinyl]thienoimidazoles were synthesized and investigated as potential inhibitors of gastricH+/K(+)-ATPase. The [3,4-d] isomers of the two possible thienoimidazole series were found to be potent inhibitors of gastric acid secretion in vitro and in vivo. Structure-activity relationships indicate that especially lipophilic alkoxy, benzyloxy, and phenoxy substituents with additional