The Third International Symposium on Immunotoxins, scheduled for June 18th-20th, 1990 at the Orlando Marriott Airport Hotel in Orlando, Florida, will provide the only forum for exchange of scientific information on the mechanism of action of peptide toxins of plant, bacterial and fungal origin and on the protein engineering design problems unique to immunotoxins for therapy of cancer, autoimmune disease, and viral disease. Specific unique aspects of this meetings will be: (1) The first presentation of the 3-dimensional structure of diphtheria toxin at an international meeting using a computer/projection system for simultaneous viewing by a large computer/projection system for simultaneous viewing by a large audience; (2) The first meeting with a session devoted to immunotoxin development including discussion of proprietary issues, manufacturing problems, regulatory issues, and clinical protocol design (There will be participation by members of the biotechnology/pharmacology industry, FDA, and academic clinical investigators.); (3) The first review of all phase II trials of immunotoxins for both malignant, viral and autoimmune diseases. The long term consequences of such a meeting are to encourage new scientists to enter the field of toxin research and to speed the development of new immunotoxins for treatment of cancer and other diseases including AIDS. This is the only forum (held every other year) which is focused on an in depth scientific study of immunotoxin research and development with over 200 participating scientists and clinicians.