A NATO Advanced Study Institute on "Phytotoxins in Plant Diseases" was held in Pugnochiuso (Italy) in June 1970. It was concerned mainly with the chemistry and mode of action of substances toxic to higher plants which are produced by pathogenic bacteria and fungi. The role of such substances in specificity was consider- ed but largely in relation to host-specific toxins. In 1973, in light of the success of the 1970 Institute, we decided to plan for...