The induction and elicitation phases of allergic contact dermatitis are very complicated processes that differ in many respects. Many issues remain to be investigated, especially in the elicitation phase of this disease. Several key molecules involved in the development and maintenance of allergic contact dermatitis have already been defined, including a number of different cytokines and adhesion molecules. Attempts are being made to develop new, more specific pharmacologic and immunologic inhibitors of their activity. Because patients who see a doctor are already sensitized, further elucidation of the factors affecting the elicitation of allergic contact dermatitis will greatly contribute to the prevention and treatment of the disease. Copyright (C) 2000 by W.B. Saunders Company.