Adhesion molecules are expressed on the surface of various cells and establish cell-cell interaction, playing important roles in development, inflammatory reaction, immune response, and tissue regeneration. Neural adhesion molecules, found on neurons or glial surfaces, are involved in the migration of neurons, neurite formation, myelination, and denervation--reinnervation. The roles of cell adhesion molecules in malignancies, normal and abnormal development and as receptors in viral infections, constitute major fields of research and may have important diagnostic and therapeutic implications.