Ethyl 2-arylhydrazono-3-oxobutyrates 6a-f, 5-(4-aminophenyl)-2,4-dihydro-4-phenyl-3H-1,2,4-triazole-3-one 5d and 1-[4-(benzoylamino)benzoyI]-4-phenylsemicarbazide 4d were synthesized in order to determine their antimicrobial properties. Their structures were elucidated using spectral data. The synthesized compounds were tested in vitro against one Gram-positive and 2 Gram-negative bacterial strains, one Mycobacterial strain and a fungus Candida albicans. Compound 6d showed significant activity against Staphylococcus aureus whereas the others had no remarkable activity on this strain. Componnd 6e was found to be more active than the others against Mycobacterium fortuitum at a MIC value of 32 mu g/mL. The antibacterial and antifungal activities of ld, 5d and 6a-f were also compared with various standard drugs. (C) Elsevier, Paris.