Procedures have been developed allowing recombinant DNA work with Clostridium acetobutylicum DSM 792. Electroporation was used to introduce plasmid DNA into exponentially growing clostridial cells and 6 x 10(2) transformants/mu g DNA could be obtained at a time constant of 5.5 ms, 1.8 kV, 50 mu F, and 600 Omega. The method also allowed the taxonomic group IV strain NI-4082 to be transformed (10(1) transformants/mu g DNA). Plasmid preparation from recombinant clostridia was optimal when a modification of the alkaline lysis method was employed. It was also important to use cells from the mid-logarithmic growth phase. Recombinant strains could be easily preserved as spore suspensions; under all conditions tested plasmids were maintained.