In the present study, relative KRAS and HRAS genes expression levels were retrospectively evaluated in 39 whole blood samples collected from patients with NSCLC at three points of time (at the time of diagnosis, 100 days and 1 year after the surgery) and in 35 tumor tissue samples obtained during operation using the real-time PCR method. The gene discussed is HRAS; the disease is non-small cell lung carcinoma.