Tocopherols are lipophilic antioxidants found in vegetable oils. Here, we examined the growth inhibitory effect of a gamma-tocopherol-enriched tocopherol mixture (gammaTmT) against CL13 murine lung cancer cells grown in culture and as subcutaneous tumors in A/J mice. We found gammaTmT had no effect after 2 days and weakly inhibited the growth of CL13 in culture after 5 days (28% growth inhibition at 80 microM). Dietary treatment with 0.1 and 0.3% gammaTmT for 50 days inhibited the growth of CL13 tumors in A/J mice by 53.9 and 80.5%, respectively. Histopathological analysis revealed an increase in tumor necrosis compared to control tumors (80 and 240% increase by 0.1 and 0.3% gammaTmT, respectively). Dietary treatment with gammaTmT dose-dependently increased gamma- (10.0-37.6-fold) and delta-tocopherol (8.9-26.7-fold) in the tumors of treated mice compared to controls. Dietary treatment with gammaTmT also increased plasma gamma- (5.4-6.7-fold) and delta-tocopherol (5.5-7-fold). Whereas others have demonstrated the cancer preventive activity of gammaTmT against mammary and colon cancer, this is the first report of growth inhibitory activity against lung cancer. Further studies are needed to determine the underlying mechanisms for this anticancer activity, and to determine if such activity occurs in other models of cancer.