BACKGROUND: Abdominal aortic aneurysm (AAA) formation involves an inflammatory process with a strong genetic background. C-reactive protein (CRP) regulates inflammation and is elevated in patients with AAA. The aim of this study was to investigate the association of the triallelic (C, A, and T alleles) rs3091244 functional CRP single nucleotide polymorphism (SNP) with AAA. METHODS: This was a case-control study involving two independent populations: 351 AAA patients (mean aortic diameter, 6.25 ± 1.47 cm) and 391 controls (mean diameter, 2.4 ± 0.2 cm) were recruited from Greece (the main cohort); and 371 patients (mean diameter, 5.4 ± 1.0 cm) and 362 controls (mean diameter, 2.4 ± 0.6 cm) were recruited from the United Kingdom (replication cohort). The frequency of the functional triallelic (C, T, and A alleles) rs3091244 polymorphism was analyzed in univariate and adjusted (for cardiovascular risk factors) analyses, assuming that the rare T and A alleles have similar functional properties (pooled analysis for T and A). Three groups were constructed: group A included those with the rare T and A alleles (genotypes TT, AA, and TA), group B included heterozygotes for the C allele (CT, CA), and group C included C allele homozygotes (CC, reference genotype). Finally, meta-analysis of the two populations was performed together with previously reported results. RESULTS: Genotype distributions differed significantly between cases and controls in both cohorts (P 5.5 cm were significantly more frequent among the SNP groups A and B compared with C allele homozygotes both in the main and the replication cohorts (P