In recent years many data indicate that lymphocytes from cancer patients undergo increased apoptosis. The objective of this study was to evaluate the expression of Fas receptor on lymphocytes obtained from patients with lung cancer. Eighteen patients with non-small cell lung cancer and 18 healthy volunteers were investigated. Expression of Fas (CD95) on CD4+ and CD8+ blood lymphocytes was evaluated by flow cytometry. The proportion of blood Fas+ lymphocytes was significantly higher in lung cancer patients when compared with healthy individuals and in smokers when compared with nonsmokers.