Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) ; Processo FAPESP: 99/05610-2 ; Processo FAPESP: 99/06094-8 ; Chronic periodontal disease (PD) is an infectious immune-inflammatory illness. Polymorphisms in IL1 genes play a role in inflammatory diseases through the modulation of cytokine levels.Objective: This study aimed to investigate the association between polymorphisms in the IL1 gene cluster and chronic periodontitis in a Brazilian population.Design: A sample of 113 subjects over 25 years (mean age 41.2) were grouped into: 44 healthy individuals, 31 subjects with moderate and 38 with severe periodontitis. DNA was obtained through a mouthwash and oral mucosa scraping. PCR-RFLP was used to identify the following polymorphisms: ILIA C - 889T (rs1800587), IL1B C - 511T (rs16944), IL1B C + 3954T (rs11436340), IL1RN intron 2 (rs2234663). Differences in the allele/genotype/haplotype frequencies were assessed by Chi-square test (p