A biochemical plant pathology seminar was held at Zyozankei, Hokkaido on August 18-20, 1965. The following progress reports were presented at this meeting. 1. Oku, H. (Sankyo Pharmacological Institute, Shinagawa, Tokyo): The physiological and chemical properties of the pathogen and their contribution to the formation of Helminthosporium leaf spot of rice. 2. Tani, T. (Faculty of Agriculture, Kagawa University, Miki, Kagawa): Studies on the pathological physiology of anthracnose of Japanese persimmon, with special reference to the role of pectic enzymes to the symptom development of the fruit. 3. Nishimura, S., Scheffer, R. P., and Nelson, R. R. (Faculty of Agriculture, Tottori University, Tottori; Michigan State University, East Lansing; North Carolina State College, Raleigh): The metabolism of victoxinine produced by the genus of Helminthosporium. 4. Otsuka, K. (Faculty of Education, Niigata University, Niigata): Biochemical studies on the physiological races of Piricularia oryzae. 5. Tomiyama, K., Sakai, R., Sakuma, T., and Takemori, T. (Hokkaido National Agricultural Experiment Station, Sapporo): The metabolism of phenolic compounds found in the tissues adjacent to the resistant lesions and their role in the resistance. 6. Toyoda, S. (the late) and Suzuki, N. (National Institute of Agricultural Science, Tokyo): The carbon metabolism of black spot fungus of pear and the mode of action of copper fungicides against the fungus. 7. Asahi, T., Verleur, J. D., Honda, A., and Uritani, I. (Faculty of Agriculture, Nagoya University, Anjo; Free University, Amsterdam): Biochemical studies on the mitochondria obtained from injured and diseased plant tissues. 8. Ouchi, S., Shishiyama, Z., and Akai, S. (Faculty of Agriculture, Kyoto University, Kyoto): The mechanism of inactivation of plant virus by ultraviolet ray. 9. Takahashi, T. and Hirai, T. (Faculty of Agriculture, Nagoya University, Anjo): Mitochondrial activity of tobacco leaves infected with tobacco mosaic virus. The discussion was mainly focused on the toxic and enzymatic substances produced by fungi and their action within host plant tissues and on the phenolic compounds and polyphenol oxidases which are found around the infected tissues. Special mention was also made on the mitochondria in potato tubers and sweet potato roots as well as in tobacco leaves, with reference to the oxidative activities.