In the present work, we compared the antitumor effects of native human interferon-α (IFN-α) (nHuIFN-α) and recombinant human IFN-α (rHuIFN-α) on human lung adenocarcinoma A549 cells. The antitumor activity was determined by measuring cell viability and apoptosis, while the abundance of mRNA, measured by polymerase chain reaction (PCR), determined the potential role of p21 and survivin in antitumor activity of nHuIFN-α. The results show that nHuIFN-α significantly reduced A549 cell viability, compared to rHuIFN-α. The most potent effect of nHuIFN-α was also observed when apoptosis was measured. A549 cells treated with nHuIFN-α expressed a significantly higher amount of p21 mRNA, while the amount of survivin mRNA was significantly reduced. Considering both the anti-proliferative and anti-apoptotic effects of each IFN-α, we conclude that further elucidation of the mechanisms of the antitumor activity of nHuIFN-α will help in producing more effective and less toxic therapeutic protocols and preparations.