Recently, we have shown that low iron state reduces benzoyl peroxide-mediated tumor promotion in murine skin. To further test the dependence of iron on skin tumor development, we assessed the effect of a low iron diet on 12-O-tetradecanoyl phorbol-13-acetate (TPA)-mediated tumor promotion in murine skin. Female Swiss albino mice were fed on a low iron diet and initiated with a single dose of 7,12-dimethylbenz[a]anthracene (DMBA, 40 μg as 150 μl per mouse) and promoted with TPA (2.5 μg as 200 μl per mouse, twice-weekly application for 20 weeks). The appearance of the first papilloma and the number of tumors (papillomas and carcinomas) per mouse were recorded weekly. We observed a decrease in tumor incidence (papillomas and carcinomas) and number of tumors per mouse in TPA-promoted mice fed on low iron diet (0.23 mg Fe/kg diet) compared to normal mice fed on balanced mouse chow (1.70 mg Fe/kg diet). The total iron consumption per day by mice being fed on balanced mouse chow was 340-400 μg Fe/kg body weight, and the total iron consumption per day by mice being fed on low iron diet was 45-55 μg Fe/kg body weight. The number of papillomas per mouse was 45% lower and the conversion of papillomas to carcinomas was about 20% lower in mice fed a low iron diet. The tumor size was also smaller in mice being fed on low iron diet. TPA treatment resulted in decreases in the activities of antioxidant enzymes and depletion in the level of epidermal reduced glutathione (GSH). Feeding mice on low iron diet along with TPA treatment resulted in ∼50-75% recovery of the depleted levels of GSH and antioxidant enzymes. In addition, TPA-mediated induction of biological markers of tumor promotion, viz. ornithine decarboxylase activity and [ 3H]thymidine incorporation into cutaneous DNA, was about 60% lower in TPA-treated mice fed on low iron diet than in normal mice treated with TPA. Cutaneous iron levels were also lower in mice fed on low iron diet than in mice fed on normal diet. Histopathological sections of the skin portion adjoining tumors showed a lower degree of epidermal hyperplasia and lesser infiltration of inflammatory cells in the dermis, and absence of hyperkeratosis in mice fed on low iron diet. Thus, in this study we observe that the tumor promoting potential of TPA is reduced in mice fed on low iron diet, which is also accompanied by lesser inflammatory changes in the skin of tumor-bearing mice fed on low iron diet. © Springer-Verlag 2004.