Allergic contact dermatitis (ACD) is one of the most common skin diseases with a great socioeconomic impact. Although extensively studied, its pathophysiology and the interaction of different cells and factors which lead to sensitization and elicitation reaction are still not completely understood, The advent of transgenic mouse technology has considerably changed the study of ACD. This technology has been used extensively to investigate biomedically important issues in such diverse areas as mammalian development, neurophysiology and immunology. This new approach has already led to fascinating results which are confirmatory but also contradictory to previous thinking on the role of certain cytokines, adhesion and cell surface molecules in the complex pathophysiologic process of ACD. This review will describe how recent experiments employing mice carrying cytokine and accessory molecule transgenes change our current understanding of contact dermatitis which may lead to improved therapeutic strategies, Copyright (C) 2000 S. Karger AG, Basel.