Ninjurin is a protein that is up-regulated in Schwann cells and neurons after peripheral nerve injury. Its role in promoting nerve regeneration and its expression in sensory neurons of dorsal root ganglia, as well as the chromosomal localization of the ninjurin gene, makes this gene a candidate for hereditary sensory neuropathies (HSN). In the present report, the human ninjurin gene was analyzed in 17 unrelated patients with HSN type I, two patients with HSN type II, and 10 normal controls, by single strand conformation polymorphism and by direct sequencing. All three exons and splice junctions of the gene were investigated and no mutations were found in our sample of patients. Our results rule out a mutation in the translated region of the ninjurin gene as a cause of HSN type I and type II.