Abstract: part of the present armory of the clinicians. The synthesis and antibacterial activity of several new ethyl 2-amino-4-methylthiazole-5-carboxylate(1)⁵derivatives substituted at 2^nd position by aryl aldehydes of the thiazole moiety have shown some to increase the antibacterial activity of thiazole. In this study we thought to synthesize thiazole system incorporating substituted aryl aldehydes. The most active compound was 4-methyl-5-hydrazine hydrate-2-(4-methoxy-3-hydroxy benzene) methyleneamino thiazole-5-carboxylate (3c) equipotent to Ciprofloxacin.C₂ position of thiazole ring requires large hydrophilic, electronegative functional moieties like substituted phenyl ring etc for enhanced antibacterial activity of thiazole. In our compounds alkyl (methyl) group is present, still most of the compounds show good antibacterial activity.C₅ position of thiazole ring requires small hydrophobic, electronegative functional moieties like amino, hydrazine hydrate attach with ester for antibacterial activity of thiazole in general.