Our previous studies of 241 re-visit outpatients in the Helicobacter pylori (HP) eradication program (HPE) of Aichi Cancer Center Hospital (Jpn J Cancer Res 2001;92:383-389 ) and of 462 health checkup examinees (HCE) in Nagoya (Jpn J Public Health 2001;48:604-612) found a significant association between HP seropositivity and the Interleukin 1B (IL-1B) C-31T genotype, especially among current smokers. This study aimed to confirm the association for 547 first-visit outpatients (277 males and 270 females) of Aichi Cancer Center Hospital aged 40 to 79 years. Samples were genotyped by polymerase chain reaction with confronting two-pair primers (PCR-CTPP), the same method as that used in the previous studies. Sex-age-adjusted odds ratio (aOR) was 1.32 (95% confidence interval, 0.84-2.08) for CT genotype and 1.35 (0.84-2.08) for TT genotype. The aOR was higher in never smokers (aOR=1.69, 0.86-3.32 for TT genotype) than in current smokers (aOR=1.01, 0.34-2.98 for TT genotype). The obtained aORs for TT genotype were inconsistent to those in our previous studies; aOR=2.46 (1.06-5.74) for 241 HPE, aOR=1.74 (1.05-2.89) for 462 HCE, aOR=22.9 (1.97-266) for 55 HPE current smokers, and aOR=4.62 (0.94-22.7) for 67 HCE current smokers. Since the 95% confidence intervals of aORs for TT genotype from the three study subjects overlapped, the inconsistent findings could be due to random errors. Alternatively, there might be other effect modifiers for the association with the polymorphism. Further studies will be required to elucidate the causes of the observed inconsistent findings.