In recent years, studies on the genotoxic effects of smoking and its modifying factors have been widely followed with interest. In this report, frequencies of micronuclei (MNF) in peripheral-blood lymphocytes in 220 healthy smokers have been detected by the micronucleus test by finger-skin puncture, which needs only 1 to 2 drops of peripheral blood. On the basis of analysis of matched-pair data, the modifying effects of alcohol and tea are discussed. Our results show that (I) smoking significantly increases MNF in lymphocytes as compared with healthy non-smokers (p less than 0.01); (2) alcohol significantly increases MNF in smokers (p less than 0.01); (3) tea decreases MNF induced by smoking (p less than 0.01). Therefore, the anti-carcinogenic role of tea merits further study.