Although it is fairly well accepted that pulmonary tuberculosis is a major risk factor of lung cancer, the exact molecular mechanisms involved in its tumorigenesis are unclear. For this purpose, we have examined the relationship between Mycobacterium tuberculosis (M-TB) infection and FHIT gene alteration in lung cancer. Tumors with M-TB infection had a slightly higher abnormal FHIT protein expression compared with tumors without M-TB infection, although not statistically significant (Fisher's exact test, P=0.248). LOH affecting at least one locus of the FHIT gene was significantly more frequent in lung cancer patients with M-TB infection than in patients without M-TB infection whether assessment by univariate testing methods or logistic regression modeling analysis (Fisher's exact test P=0.025, logistic regression analysis P=0.012). These results indicate that M-TB infection is associated with FHIT gene LOH in lung cancer.