Series of compounds N’-[(3-Substituted alkyl/aryl)-4-(substituted aryl)-1,3-thiazol-2-ylidene]-4- hydroxybenzohydrazide (10-37) were designed via 3D-QSAR studies. These compounds were synthesized by reacting compounds (3-9) with various substituted phenacyl bromides in presence of sodium acetate. Good yield of compounds (10-37) were obtained by established reaction. Structure of newly synthesized compounds were evaluated on the basis of spectral data. These compounds (10-37) were tested in vitro against species of grampositive bacteria, Staphylococcus aureus (ATCC 3750) and Bacillus subtilis (ATCC 6633), and gram-negative bacteria, Salmonella typhi (NCTC 786) and Escherchia coli (ATCC 25922). The minimum inhibitory concentration (MIC) was determined by the tube dilution technique using modified Muller-Hinton agar culture medium. Among the compounds tested, the compound (23) N'-[4-(2,4-dichlorophenyl)-3-(4-nitrophenyl)-1,3-thiazol-2(3H)-ylidene]- 4-hydroxybenzohydrazide had shown highest antimicrobial activity against gram-positive and gram-negative organisms while other compounds (19) N'-[3-(4-chlorophenyl)-4-(2,4-dichlorophenyl)-1,3-thiazol-2(3H)-ylidene]-4- hydroxybenzohydrazide, (16) N'-[4-(2-chloro-4-methylphenyl)-3-(4-fluorophenyl)-1,3-thiazol-2(3H)-ylidene]-4- hydroxybenzohydrazide and (25) N'-[4-(2-chloro-4-hydroxyphenyl)-3-(4-nitrophenyl)-1,3-thiazol-2(3H)-ylidene]-4- hydroxybenzohydrazide, also showed good antimicrobial activity against gram-positive and gram-negative organisms. The results of antimicrobial activity were compared with standard antibiotics (ampicillin, penicillin-G, chloramphenicol).