The interleukin-1 system is fundamentally involved in the pathogenesis of restenosis after percutaneous transluminal angioplasty (PTA). In order to further define the clinical impact of genetic variation in this potent proinflammatory pathway we investigated the joint effects of two single nucleotide polymorphisms in the interleukin-1 beta gene [IL-1B(-511) and IL-1B(+3954)] and a variable number tandem repeat polymorphism in intron 2 of the interleukin 1 receptor antagonist gene (IL-1RN VNTR) on postintervention inflammation and occurrence of restenosis in 183 consecutive patients who underwent successful femoropopliteal PTA. C-reactive protein (CRP) and serum amyloid A (SAA) were determined pre- and 48 hours postintervention. Patients were followed up to 12 months for the occurrence of postangioplasty restenosis (> or = 50%). When analyzed separately, none of the polymorphisms was associated either with inflammation or restenosis. However, when the IL-1B (-511) and the IL-1RN VNTR genotypes were combined, a highly significant relationship was observed: Non-carriers of the two repeat allele of the IL-1RN VNTR (IL-1RN*2) who were heterozygous and homozygous for the IL-1B (-511)T allele exhibited a gradually increased inflammatory response and a higher restenosis risk. In contrast, carriers of the IL-1RN*2 and the IL-1B (-511)T allele showed a significantly better outcome. This remarkable gene dose-dependent association emphasizes the advantage of considering combinations of genetic markers rather that isolated polymorphisms in the analysis of multifactorial vascular disease.