2-Amino-5-methyl-1, 3, 4-thiadiazole, 2-chloro-N-(5-methyl-1, 3, 4-thiadiazol-2-yl)acetamide, 2-imino-3-(5- methyl-1 ,3, 4-thiadiazol-2-yl)thiazolidin-4-0ne and new seven 5-arylidene-2-imino-3-(5-methyl-1, 3, 4 thiadiazol-2-yl)thiazolidin-4-one compounds have been synthesized starting from thiosemicarbazide and acetic acid. The structures of these compounds have been confirmed by IR, 1H-NMR and HR-MS spectral data. At concentration of 0,5 percent, all of the 5-arylidene-2-imino-3-(5-methyl-1,3,4-thiadiazol-2-yl)thiazolidin-4one compounds showed moderate antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus.