We studied membranotropic effect of dammarane-type triterpenes (isolated from birch leaves) with a variable side chain structure, as well as the number and configuration of OH groups as a function of temperature and pH. Polyols with an acyclic side chain and four OH groups proved to have a higher hemolytic activity as compared to polyols with three or five hydroxyl groups. The triterpenes, with tetrahydrofurane cycle as the side chain, exert a hemolytic effect at a more acidic pH (5.0) and higher temperature (45 degrees C), as compared to the polyols with acyclic side chain. Irrespective of the side chain structure, the compounds with a 24(S) configuration lysed the erythrocytes at lower rate, as compared to the compounds with a 24(R) configuration.