22 patients with advanced non-small-cell lung cancer were randomized to receive chemotherapy (ifosfamide) or chemotherapy followed by thymosin α1 + low-dose IFNα. Chemo-immunotherapy induced an enhanced response rate compared with chemotherapy alone (33% and 10% respectively). Although these differences were not significant, the difference in time to progression was (p = 0.0059). CD4+, CD8+ and NK cell counts were significantly depressed after two cycles of chemotherapy, while no difference in cell count were seen in chemo-immunotherapy treated patients. Hematologic toxicity was reduced by the immunotherapy, with no grade 3/4 toxicity seen compared to 50% in patients treated with chemotherapy alone.