We examined the effect of propolis granular A. P. C on lung tumorigenesis in female A/J mice. Lung tumors were induced by the tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) administered in drinking water for 7 weeks in mice maintained on an AIN-76A semi-synthetic diet. Propolis granular A. P. C (100 mg/kg body wt.) was administered orally daily for 6 days/week from 1 week before NNK administration and throughout the experiment. Sixteen weeks after the NNK treatment, the mice were killed and the number of surface lung tumors was measured. The number of lung tumors in mice treated with NNK alone for 7 weeks (9.4 mg/mouse) was significantly more than in that observed in control mice. Propolis granular A. P. C significantly decreased the number of lung tumors induced by NNK. These results indicate that propolis granular A. P. C is effective in suppressing NNK-induced lung tumorigenesis in mice.