Agroinfiltration consists in the transient delivery of recombinant genes to plant cells to obtain recombinant gene expression without stable integration or transmission to the offspring. Agrobacterium is used as a delivery vehicle and often involves a self-replicative genetic device to enhance extension and productivity. When Agrobacterium cell cultures are infiltrated into the intercellular spaces of leaf parenchyma, the transfer of T-DNA into the plant cell nucleus becomes a highly efficient event. The most popular host plant for agroinfiltration is Nicotiana benthamiana; however, the power of the technique has been also described for other species like lettuce, tomato or Arabidopsis. Agroinfiltration is often used as delivery system for replicons that either move systemically (viral RNA genomes) or amplify locally. In the context of molecular farming, large-scale agroinfiltration of N. benthamiana is used as a fast and efficient system for recombinant protein production.