The study of disease entities as complex as Crohn's dis ease will increasingly require comprehensive knowledge of formerly unrelated areas of the medical sciences. To promote this broad approach, a conference was organized in which geneticists, morphologists, immunologists, and virologists participated as well as clinicians whose work is focused on Crohn's disease. Ample time was given to the presentation of major new findings in each of these areas, and comments were given by the participants in the various sections. This approach yielded many new ideas, because indiv iduals with very...