Several diseased plants affected with varied pathogens (downy mildews, powdery mildews, rusts, leaf spot fungi) and with some viruses were inserted into the radioactive phosphorus-32 solution and the accumulation at the leaf lesions of radioactive phosphorus absorbed through roots was followed by means of autoradiograph. On the other hand starch accumulation at those lesions was investigated by Jode-jode kali reaction. There was a greater accumulation of the phosphorus-32 in the diseased than in the healthy tissue in 16 host-pathogen combinations, lesser accumulation or no clear difference in 12 cases. Interrelation between radioactive phosphorus-32 accumulation and that of starch at the lesions caused by pathogenic organisms was observed with one or two exceptons, while no interrelation was found in the case of the necrotic lesions caused by the viruses (TMV, CMV, and potato virus X).