A number of beta-propiolactone homologue were synthesized and their bactericidal and fungicidal action studied. It was established that bactericidal action of beta-propiolactones is connected with cleavage of the lactone ring by water hydrolysis, which leads to formation of a mobile hydrogen atom of the alcohol group of the respective beta-oxy acids. Simultaneous introduction of two methyl radicals and a methyl group and an ethyl one to the beta-position of propiolactone was shown to enhance bactericidal action of the appropriate homologue. A +l-inducible effect of the beta-substituents of beta-propiolactone hydrogen atoms on enhancement of bactericidal action is discussed as well as the influence of increasing hydrophobicity and branching of beta-propiolactone homologue on the smoothing of bactericidal action. (C) 2003 Elsevier Ltd. All rights reserved.