p53 protein, which accumulates intracellularly in over half of all human tumors, has been reported to be variably present in the sera of patients with various malignancies. In this study, it was aimed to detect p53 protein in the sera of lung cancer patients, and to verify its value as a marker of p53 alterations in lung cancer. A pantropic quantitative ELISA technique was used to detect serum p53 protein of 94 newly diagnosed patients with lung cancer. Serum samples were collected on admission before any treatment. There was no detectable serum p53 protein in the control group including 34 healthy volunteers. Serum p53 protein was present in only 3 (3.2%) of 94 patients. In nonsmall cell lung cancer (NSCLC) group, serum p53 protein had been detected in 2 (2.8%) of 72 patients, and it was detectable in 1 (4.5%) of 22 patients in SCLC group. Serum levels of p53 protein ranged from 1 U/mL to 31.25 U/mL in positive samples. Patients who had p53 protein in their serum samples, were at late stage and had poor prognosis. In conclusion; prognostic value of detectable serum p53 protein levels could not be define, because of the small number of p53 positive patients. The use of quantitative serum p53 protein analysis with ELISA is of very limited value as a marker in evaluating p53 changes in lung cancer patients, despite the fact that is an easy technique to perform.