A series of α,β-unsaturated and α-bromo carboxylic acids were iden- tified as potent antimicrobial agents. The antimicrobial activity was evaluated using the broth microdilution method. All acids 1-12 exhibited a significant activity against nine laboratory control strains of bacteria and two strains of yeast Candida albicans. The tested acids were efficiently prepared by opti- mized phase-transfer-catalyzed