Recombinant rotavirus VP6 expressed in transgenic tomato cells was found primarily in the intracellular fraction and had a molecular weight of 44 kDa. In a shake flask, transgenic tomato cells produced 0.33 mg recombinant VP6 l(-1) after 18 days of incubation. In a high aspect rotating-wall vessel designed by NASA to simulate microgravity, the transgenic cells produced up to 0.15 mg recombinant VP6 l(-1).