New 2,5-disubstituted 1,3,4-oxadiazoles derived from amino acids carrying phenyl group at position (2) and benzamido, alkyl moieties at position 5 which were synthesized as outlined below : 1. Synthesis of benzamido carboxylic acid [1-5]:- Condensation of appropriate amino acid (p- amino benzoic acid, o- amino benzoic acid, valine, leucine, phenyl alanin) with benzoyl chloride gave the corresponding benzamido carboxylic acids, having the following structure formula as mentioned in the orginal abstract 2.Synthesis of 2,5-disubstituted-1,3,4-oxadiazoles [6-10] Reaction of appropriate benzamido carboxlic acid with benzoyl hydrazine in the presence of phosphorous oxychloride furnished the corresponding 2,5-disubstituted 1,3,4-oxadiazoles [6-10] having the structural formula mentioned in the original abstract .The biological activity of the synthesized compounds [1-10] for their antimicrobial activity against two strains of pathogenic microorganism Gram positive bacteria Staphylococcus aureus and Gram negative bacteria Escherichia coli. Antifungal activity were also evaluated against Trichophytone rubrum. And finally, the cytotoxic effect were evaluated in normal cell line (Mouse embryo fibroblast) after 72 hrs of incubation. The results obtained revealed that all compounds showed measurable activity against the two type of bacteria using two concentration (0.005g/5ml ) and (0.008g/5ml). The screening results indicated that compounds [8] and [10] showed the highest inhibitory effect against S. aureaus while compounds [1] and [5] showed the highest inhibitory effect against E. coli . While in the fungus, The synthesized compounds showed an inhibition effect on the growth of T. rubrum. The inhibition of T. rubrum appeared at concentration (0.005g/5ml) except compounds [3] and [4] to which the pathogenic fungus was resistant in the same concentration. For the cytotoxic effect, the synthesized compounds indicated that the compounds [1-5 and 10] have weak cytotoxic effect in lowest concentrations compared with solvent and control, and the compound [5] showed the highest cytotoxic effect on the treated cells, while compounds [6-9] have no cytotoxic effect in all concentrations.