The present study was undertaken to estimate the effect of 7-hydroxy-3-methoxycadalene (cadalene) extracted from Zelkova serrata on 4-(methylinitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in A/J mice. Twenty mice received orally NNK at a dose of 65 microg/ml water for 7 weeks following by free feeding of a commercial diet not containing cadalene for 2 weeks. Control group was maintained without NNK and cadalene administration and/or treatment groups with NNK and cadalene (6.25, 25, 100 mg/kg feed) feeding for 25 weeks. Lung tumors were induced by NNK at incidence ranging from 10 to 45%. Cadalene treatment (100 mg/kg feed) group significantly reduced the incidence of adenomas from 45 to 10% (P < 0.05), and other cadalene treatment group decreased cancer incidences in a concentration dependent manner. The results of our study strongly indicate that cadalene is capable of inhibiting development of NNK-induced lung tumorigenesis in A/J mice.