The present invention relates to methods for expressing proteins of interest, particularly pharmaceutically valuable proteins, transiently in plants. In particular, the invention provides an improved method for introducing Agrobacterium cells into a whole plant or a plant organ. The methods of the invention provides efficient agroinfiltration of many plants singly or simultaneously resulting in a yield of recombinant proteins that is higher than that obtained by other methods. The methods can be readily scaled and automated to meet changing demands of the recombinant protein.
