Interleukin-1 (IL-1) has been implicated in the pathogenesis of rheumatoid arthritis (RA). We investigated whether IotaL-1 gene locus polymorphisms are associated with susceptibility to or severity of RA. Genotyping for IL-1alpha, IL-1beta and IL-1Ra single nucleotide polymorphisms (SNPs) performed in a cross-sectional group of 312 consecutive RA patients (RA-group 1) and a cohort of 94 incident female RA patients (RA-group 2) revealed that the rare IL-1RN + 2017 C allele was significantly increased in RA compared to controls (n = 245). A retrospective analysis in RA-group 1 showed no significant associations between IL-1 genotypes and disease severity. A prospective study in RA-group 2 demonstrated that the extent of joint destruction over 12 years was higher in patients genotyped heterozygous for the IL-1 A + 4845, IL-1B + 3953 and IL-1RN + 5111 SNPs compared to homozygous wildtype patients, although differences did not reach statistical significance. These data indicate that the IL-1RN + 2017 polymorphism is associated with susceptibility to RA.