After chemical modification preceded by the random screening of our chemical library, a novel class of selective anti-Helicobacter pylori agents was generated. Consequently, the 3-(arylacetylamino)-N-methylbenzamides, which were quite easy to prepare, showed potent inhibitory activity against Helicobacter pylori but exhibited no inhibitory activity against other sorts of bacteria and fungi, e.g., Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Bacteroides fragilis, and Candida albicans. These compounds showed potent anti-H. pylori activity under acidic conditions, whereas amoxicillin and clarithromycin decreased activity. The 3-(3-arylpropionylamino)-N-methylbenzamides, 3-(aryloxyacetylamino)-N-methylbenzamides, and (3-methylcarbamoylphenyl)carbamic acid 1-arylmethyl esters also exhibited potent anti-H. pylori activity. Finally, we selected 7n (BAS-118) as a candidate compound for further evaluation.