Agroinoculation refers to the introduction of genetic information from plant viruses into leaves or other organs of the host plant through Agrobacterium tumefaciens. Agroinoculation of geminiviruses requires the insertion of tandem copies of the genome between the T-DNA borders of an Agrobacterium binary vector. The technique is applicable to most plant species and is limited only by the host range of the virus and of the A. tumefaciens strain. Herbaceous plants can be easily agroinoculated using a needleless syringe. The successful agroinoculation of plants with begomoviruses involves the preparation of A. tumefaciens competent cells, the transformation of A. tumefaciens with the cloned tandem copy of the viral genome, and the agroinoculation procedure itself. This chapter describes a straightforward protocol for the agroinoculation of a cloned infectious begomovirus into plants.