Because cell-cell and cell-matrix interactions directly affect the growth, differentiation, and morphogenesis of neural tissue, abnormal changes in these processes could have severe pathologic consequences. Over the last few years, it has become possible to investigate these interactions at the molecular level due to advances in the identification and characterization of matrix components and receptors and cell adhesion molecules (CAMs). Emerging evidence suggests that two broad classes of CAMs are represented by the neural CAM, N-CAM, and the epithelial CAM, L-CAM. N-CAM and several other neural adhesion molecules contain immunoglobulin-like domains and do not require calcium for binding. In contrast, L-CAM, N-cadherin, and P-cadherin depend on calcium for activity and share structural features that differ from those of the N-CAM family. All of these CAMs are expressed in early embryos and in a variety of tissues throughout development, although each has a characteristic pattern. Initial studies suggest that injury, oncogenic transformation, and some genetic neurologic disorders are accompanied by changes in CAM expression that alter the adhesive or migratory behavior of cells.