According to recent analyses of complete genome sequences horizontal gene transfers have played a fundamental role in bacterial evolution. Nowadays, this is efficiency of bacteria in picking up genes of surrounding organisms that rises concerns about a potential dissemination of genes from transgenic plants to soil bacteria. The only mechanism which could be involved for such gene exchanges is natural transformation which requires the successive occurrence of several steps, including release of plant DNA, persistence of DNA in the environment, presence of transformable bacteria and internalization of the sequences in the new host. The data I present in this paper indicate that transformation-mediated gene transfers could occur in the environment and in the case of transgenic plants are more likely to involve the prokaryotic sequences of the transgene than the remaining of the genome. However, soil bacteria use to exchange genes by conjugation at frequencies several orders of magnitude higher than those resulting from a transfer from plants. One can thus assess that ecological consequences of interkingdom transfers of plant genes, naturally present in soil bacteria and which do not modify the fitness of the recipient microorganism would remain negligible.