Basipetal transport of various substances through half-inch stem sections of healthy and aster yellows virus-infected Nicotiana rustica L. var. humilis was determined. The effects of infection by three strains of the virus, dwarf, severe, and Tulelake were observed on the transport of 14C-labeled beta-indoleacetic acid, malic acid, succinic acid, sucrose, glucose, mannose, and the ions sulfate, phosphate, and rubidium. Transport of all these substances except phosphate ion was more rapid through diseased than through healthy stem sections. In the dark, and with supplementary auxin, transport of phosphate ion was also more rapid through diseased than through healthy stem sections. Transport of beta-indoleacetic acid and of sugars through healthy stem sections was more rapid in the dark than in the light, but transport of these compounds through diseased stem sections was unaffected by light. No appreciable chemical conversion of the substances tested was observed during the transport time used.