Abstract: A new series of ten compounds of  1,3,4-oxadiazoles  were  synthesized  by  ring  closure  reactions  of  different acid hydrazides with carbon disulphide and aromatic acids separately. Further, the 2-thio oxadiazoles were treated with aromatic amines to get mannich bases. The structures of the synthesized compounds were consistent with      IR, 1H NMR  and  MASS  spectroscopy.  The synthesized  compounds  were  screened  by  disc  diffusion  method  for their antibacterial and antifungal activity. Among the compounds synthesized 3d,  3e  and  5b  shown significant antimicrobial activity against both bacterial and fungal strains.