Human neurite outgrowth inhibitor (NOGO) cDNAs encodes 3 splice variants: NOGOA, NOGOB and NOGOC. The longest cDNA, designated NOGOA, has an open reading frame of 1192 amino acids. It is a potent inhibitor of neurite growth and an IN-1 antigen produced by oligodendrocytes, and may allow the generation of new reagents to enhance CNS regeneration and plasticity. Nogo-A, a member of the Reticulon family, is expressed by oligodendrocytes and associates primarily with the endoplasmic reticulum. The acidic amino terminus of Nogo-A is detected at the cytosolic face of cellular membranes and may contribute to inhibition of axon regeneration at sites of oligodendrocyte injury. A multivalent form of the N terminus of Nogo-A affects the morphology of both neurons and other cell types.