We describe a simple and efficient protocol for regeneration-transformation of two diploid Medicago lines: the annual M. truncatula R108-1(c3) and the perennial M. sativa ssp. falcata (L.) Arcangeli PI.564263 selected previously as highly embryogenic genotypes. Here, embryo regeneration of R108-1 to complete plants was further improved by three successive in vitro regeneration cycles resulting in the line R108-1(c3). Agrobacterium tumefaciens-mediated transformation of leaf explants was carried out with promoter-gus constructs of two early nodulins (MsEnod12A and MsEnod12B) and one late nodulin (Srglb3). The transgenic plants thus produced on all explants within 3–4 months remained diploid and were fertile. This protocol appears to be the most efficient and fastest reported so far for leguminous plants.