The functional units in most inductive and morphogenetic processes in the embryo are not single cells, but rather collectives of interacting cells that give rise to the tissues and organs. Cell adhesion molecules (CAMs) are involved in defining cell collectives and their borders as they interact during inductive events in morphogenesis. The expression patterns of CAMs are highly dynamic and changes are known to occur during epithelial-mesenchymal transformations. Alterations in CAM expression are correlated with changes in morphology. Conversely, experimentally induced changes in morphology result in changes in CAM expression. The structure, function, distribution, and control of CAM gene expression are presented in this review, and discussed with regard to their importance to normal developmental processes, particularly epithelial-mesenchymal transformations.