One of the main attractions of research into hypersensitivity disorders is that it brings together scientists from a very broad range of disciplines. As the most common hu man immunologic disorder, it excites the interest and concern of clinicians, geneticists, basic and clinical immunologists, molecular biologists, biochemists, and physiologists. General agreement has been forged on the the pathophysiology of the disease and the mechanisms responsible for its maintenance, but many areas remain as black boxes for which we have only hypotheses. In 1992 Vienna hosted an international symposium to consider the explosion of in formation being generated by the identification, cloning, and expression of common envi ronmental allergens: The present second international conference on the MOLECULAR BIOLOGY OF ALLERGENS AND THE ATOPIC IMMUNE RESPONSE, again jointly organized and co-chaired by Professors Alec Sehon (Winnipeg) and Dietrich Kraft (Vi enna), provided an exciting opportunity for many leaders in this field to share data, argue hypotheses and seek future opportunities to enlarge our understanding of these very com plex diseases. This symposium was co-sponsored by the International Union of Immu nological Societies (I. U. I. S. ) and the International Association of Allergology and Clinical Immunology. It was held in the hospitable and comfortably elegant surroundings of Que bec City.