Transmigration of neutrophils across epithelial surfaces is the hallmark of inflammatory mucosal diseases of diverse organs. In disorders such as Crohn's disease, ulcerative colitis, pyelonephritis, and bronchitis, for example, neutrophil transmigration correlates with clinical disease activity, is associated morphologically with injury to the epithelium, and is central to disease pathophysiology. The mechanisms by which neutrophils transmigrate across epithelia are, therefore, of considerable significance for numerous pathologic states. In this paper, we discuss current evidence that defines these mechanisms in intestinal epithelium, emphasizing the structural constituents determining adhesive interactions and a subset of the complex regulatory signals between neutrophils and epithelium.