Blackleg and soft rot diseases, caused by the bacterium Erwinia carotovora, are among the diseases that cause important losses in culture and storage of potato. In this paper, we introduced bacterial resistance into potato, via genes encoding for proteins with antibacterial activity. For this purpose, potato clones were transformed either with the gene encoding the acidic attacin protein from Hyalophora cecropia, or with the gene encoding the cecropin analog peptide SB37. These clones were evaluated for soft rot and blackleg resistance, after inoculation with the bacterial strain Erwinia carotovora subsp. atroseptica T7. Results reported in this paper indicate that a considerable percentage of the potato clones (15-22%) showed increased resistance to bacterial infection, revealed by reduced severity of blackleg or soft rot symptoms. Expression of the transgenes was demonstrated in some of the clones by Northern blot analysis. This is the first report indicating that expression of the gene encoding for an attacin protein and for the cecropin SB-37 peptide in transgenic potato confers increased resistance to bacterial infection.