A new group of low-molecular weight channel-forming oligo(hydroxybutyric acids) (cPHBs, 1 with n = 8-30; main component MW approximate to 1300 dalton) was isolated from microorganisms of different origin. Inclusion bodies were electron-microscopically visible in cells in the state of autolysis, not. in cells in the exponential phase of growth.. cPHB and high-molecular poly(beta-hydroxybutyric acid) (sPHB) is cleaved by phenylethylamine and forms the corresponding monomeric hydroxybutyramide and - under drastic conditions, the crotylamide. One of these compounds; the 3-hydroxy-N-phenethyl-butyramide (5), was isolated as a new natural product now.