The pre and para-treatment values of NSE were evaluated in 55 Small cell and 41 non-Small cell lung cancer cases who were admitted to the Medical Oncology Dept. of Istanbul University. Institute of Oncology. In comparison with the control group the NSE levels were highly significant in SCLC (0.01>p>0.001). There was no significant difference between the controls and NSLCL (p)0.5) group but NSE levels were also significant in SCLC group in comparison with the NSCLC group (0.05>p>0.02). It was also shown that NSE can be used to monitor the treatment as a prognostic indicator.