Chronic periaortitis (CP) is a rare disease characterized by a fibro-inflammatory tissue surrounding the abdominal aorta, and includes non-aneurysmal [idiopathic retroperitoneal fibrosis (IRF)] and aneurysmal forms [inflammatory abdominal aortic aneurysm (IAAA)]. We investigated whether CC chemokine receptor 5 (CCR5)Δ32 polymorphism confers susceptibility to CP.One hundred CP patients and 180 healthy controls were genotyped for CCR5Δ32 polymorphism by molecular methods. The patients were subgrouped according to the type of CP (IRF or IAAA) and the presence of established atherosclerotic disease (ischaemic heart disease, cerebrovascular disease and peripheral arterial disease).The distribution of the CCR5Δ32 genotype differed between CP patients and controls (P = 0.01). The CCR5Δ32 allele was more frequent in CP patients than in controls [P = 0.02, odds ratio (OR) 2.8 (95% CI 1.2, 6.4)]. The distribution of the CCR5Δ32 genotype did not differ significantly between IRF patients and controls, whereas the CCR5Δ32 allele was more frequent in IAAA patients than in controls [P = 0.0001, OR 10.0 (95% CI 3.7, 27.3)]. Furthermore, the CCR5Δ32 allele occurred more frequently in IAAA than in IRF patients [P = 0.001, OR 6.4 (95% CI 2.1, 19.1)]. The CCR5Δ32 allele frequency was higher in IAAA patients without established atherosclerotic disease compared with controls [66.7 vs 5.6%, P = 0.00001, OR 34.0 (95% CI 7.4, 156.3)], but not in IAAA patients with atherosclerotic disease and IRF patients with or without atherosclerotic disease.The CCR5Δ32 polymorphism might be associated with an increased risk of developing the aneurysmal form of CP, IAAA, particularly in patients without established atherosclerotic disease. Chemokines may have a role in the pathophysiology of CP.