Neuron Specific Enolase (2-phospho-D-glycerate hydrolase) is an isoenzyme that belongs to the enolase family (homo- and heterodimer constituted of α, β and γ subunit) that is distingued from these by the presence of the specific γγ heterodimer. The clinical usefullness of hNSE like tumor marker is compared to non small cell lunge cancer (NSCLC), to neuroblastoma, to medullary carcinoma of the thyroid, pancreatic islet cell tumor and to non neoplastic condition of neuronal disease and cerebral trauma. The hNSE ELISA test cannot be used as a screening test for neuroendocrine tumors, but may be used to follow levels in established diagnosis.