Electroporation gives high efficiency of transformation in Salmonella typhimurium LT2, yielding 108–109 electrotransformants per microgram of pBR322 DNA. Lipopolysaccharide (LPS) composition has little influence on electrotransformation efficiency by electroporation, unlike Ca2+ shock methods, which give ca. 106 transformants/μg DNA with strains with Rc or Rd2 LPS, 104 transformants with most smooth and rough strains, and 102 transformants with strains with Re LPS. Thus cell envelope properties are less crucial in electrotransformation than in Ca2+ shock methods. The reciprocal restriction barrier between Escherichia coli K-12 and S. typhïmurium LT2 reduces electrotransformation by ca. 100-fold, but host-restriction mutants reduce or eliminate the barrier. Key words: electroporation, Salmonella, genetics, transformation.