A method for transformation of Erwinia carotovora subsp. carotovora cells has been developed. Transformants of E. carotovora RC 5297 (pECL 18) have been obtained. The transformation frequency was 5.4 x10(2) per 1 microg of DNA. This value depends considerably on the culture growth stage and the amount of calcium chloride used for obtaining the competent cells. The spontaneous loss of the plasmid is below 0.1% per one generation of cells. Both the plasmid and the host RM-systems behave autonomously, i.e., they restrict the development of phages independent of each other. Results obtained are a precondition for creating vectors based on E. carolovora being nonpathogenic for people, endogenic and exogenic plasmids.