Interleukin (IL)-1 gene polymorphisms are associated with development of gastric atrophy and with increased risk of gastric carcinoma. A -31C to T base transition in the promoter region of this gene is involved in carcinogenic changes within the stomach, especially in Helicobacter pylori infected individuals. We examined association between IL-1 locus polymorphisms and risk of esophageal, gastric and colorectal carcinomas in Japanese patients with H. pylori infection. IL-1B and IL-1RN polymorphisms were analyzed in 136 controls, 75 patients with esophageal carcinoma, 186 patients with gastric carcinoma, 69 patients with colorectal carcinoma, and 18 patients with ulcerative colitis (UC). For IL-1B-511 and -31 polymorphisms were determined by fluorescence-based polymerase chain reaction single-strand conformation polymorphism analysis. For IL-1 receptor antagonist gene (IL-1RN), penta-allelic variable number of tandem repeats (VNTR) was determined by PCR-standard agarose gel electrophoresis. For gastric carcinoma, IL-1B-511 heterozygotes (OR, 0.48; 95% CI, 0.3-0.9; p=0.0115) and T carriers (OR, 0.52; 95% CI, 0.3-1.0; p=0.0185) had a significantly reduced risk of carcinoma. For colorectal carcinoma, IL-1B-511 heterozygotes (OR, 0.34; 95% CI, 0.2-0.7; p=0.0028) and T carriers (OR, 0.43; 95% CI, 0.2-0.9; p=0.0015) had a significantly low risk of carcinoma. No significant difference was observed in the frequencies of IL-1B-31C/T and IL-1RN genotypes between controls and the esophageal carcinoma patients. Our results shows that IL-1B-511C/T and T carrier state may indicate less risk for gastric and colorectal carcinoma in the Japanese population.