Thiazole derivatives 2a-c were synthesized via reaction of 2-chloro-N-phenylacetamide (1) and thiourea, thiosemicarbazide or thioacetamide in alcoholic potassium hydroxide. Also, substituted benzaldehyde reacted with thiosemicarbazide at reflux temperature in ethanol to afford hydrazone compounds 3a-k. Under microwave irradiation (M.I., 100W) with neat for 20sec; arylketones, thiosemicarbazide and chloroacetylchloride were reacted to afford thiazole derivatives 4a-j. Compounds are characterized by physical measurements, NMR and infrared spectra. Antibacterial activity of new compounds was evaluated with Gram Negative Serratia marcesence, Proteus vulgaris, Escherichia coli and Psudomonas aeruginosa and Gram Positive; Staphylococcus aureus in comparison with Norfloxacin and Ciprofloxacin as standard drugs.