In order to find a new class of anti-Helicobacterpylori (H. pylori) agents, a series of 4-[(3-acetamido)phenyl]-2-(substituted guanidino)thiazoles and some structurally rigid analoges were synthesized and evaluated for antimicrobial activity against H. pylori. Among the compounds obtained, high anti-H. pyrori activities were observed in benzyl derivative 34 (MIC = 0.025 microg/mL) and phenethyl derivatives