Reviews recent basic research into IgE, mast cells, and the allergic response and the relevance of this work to human pathophysiology, and discusses new methods of treatment. This symposium is unique in the IgE field for its breadth of coverage and interdisciplinary nature, and it shows the benefits from the current rapid expansion of knowledge in cell biology, immunology, and molecular genetics, as well as the potential clinical significance of this research to clinical immunologists and allergologists.