One of burgeoning fields of biology is the use of transgenic plants for the expression of antibodies. It refers to introducing into plants and expressing in them the genes encoding antibodies or antibody fragments. The plant-derived antibodies can serve the fuction of antigen recognition and binding. A number of transformation techniques have been used to introduce antibody genes into plant cells. An important advantage of expressing antibodies in plants is that it can produce inexpensively therapeutic antibodies in large scale. Immunotherapy can also be aimed at plants themselves, that is, these recombinant antibody molecules can be effective in insect or disease resistance. Furthermore, intracellular expression of antibody molecules can be used to modulate the metabolism of the expressing cells. Several groups have expressed antibody molecules in plants, either to modify or improve plant performance and characteristics or with a view to harnessing plants as bioreactors for large-scale production of antibodies. The research and development of expressing antibodies in plants are reviewed.