A series of 8-[(2-benzimidazolyl)sulfinylmethyl]-1, 2-dihydroquinolines (XIIIa-g) was synthesized and tested for (H+ + K+) adenosine triphosphatase (ATPase)-inhibitory and antisecretory activities. These compounds were synthesized by the oxidation of sulfides, which were obtained from the reaction of 8-chloromethyl-1, 2-dihydroquinolines (XIa-c) and 2-mercaptobenzimidazoles in the presence of sodium hydride. The key intermediates, 8-hydroxymethyl-1, 2-dihydroquinolines (IVa-c), were perpared by the reduction-alkylation of 8-acetoxymethyl- or 8-hydroxymethylquinolines with sodium cyanoborohydride-formic acid. Among XIIIa-g, the 1, 4-dimethyl-1, 2-dihydroquinoline derivative (XIIIa) was found to have the highest activity.