A series of novel 4-arylazo-3-methylthiophenes was synthesized by the heterocyclization of 2-arylhydrazono-2-acetyl thioacetanilide derivatives with a variety of alpha-halogenated reagents, such as chloroacetone, phenacyl bromide, ethyl chloroacetate, and chloroacetonitrile. The structures of the synthesized thiophene derivatives were confirmed by ultraviolet-visible, IR, and (1)H-NMR spectroscopic techniques and elemental analysis. The synthesized dyes were applied to polyester fabrics as disperse dyes, and their fastness properties were evaluated. The dyed polyester fabrics displayed antibacterial efficacy against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 83-89, 2011