A new 2-[(4-substituted-phenyl-3-chloroazetidin-2-one)-5-(2'-methylamino 4-phenyl-1', 3'-thiazolyl-]-1, 3, 4-thiadiazoles, 5(a-n) were synthesized from 2-substituted-benzylideneamino-5-[2'-methylamino-4'-phenyl-1',3'-thiazolyl]-1,3, 4-thiadiazole, 4(a-n) using 2-amino-4phenyl-1, 3-thiazole as a starting material. The synthesised compounds have been screened in vitro for their antimicrobial activity against Bacillus subtilis, Escherichia coli. Klebsiella pneumoniae and Streptococcus aureus bacteria and Aspergillus niger, Aspergillus flavus, Fusarium oxisporium and Trichoderma viride fungi respectively. Some of the compounds displayed pronounced biological activity.