['In patients undergoing endovascular aneurysm repair (EVAR), the postimplantation syndrome (PIS), comprising fever and inflammation, occurs frequently. The cause of PIS is unclear, but graft composition and acute thrombus formation may play a role. The objective of this study was to evaluate these possible causes of the inflammatory response after EVAR.', 'One hundred forty-nine patients undergoing elective EVAR were included. Implanted stent grafts differed mainly in the type of fabric used: either woven polyester (n=82) or expanded polytetrafluorethylene (ePTFE; n=67). Tympanic temperature and C-reactive protein (CRP) were assessed daily during hospitalization. PIS was defined as the composite of a body temperature of ≥38°C coinciding with CRP>10 mg/L. Besides graft composition, the size of the grafts and the volume of new-onset thrombus were calculated using dedicated software, and results were correlated to PIS.', 'Implantation of grafts made of polyester was associated with higher postoperative temperature (P<.001), CRP levels (P<.001), and incidence of PIS (56.1% vs 17.9%; P<.001) compared to ePFTE. After multivariate analysis, woven polyester stent grafts were independently associated with an increased risk of PIS (hazard ratio, 5.6; 95% confidence interval, 1.6-19.4; P=.007). Demographics, amount of graft material implanted, or new-onset thrombus had no association with PIS.'] Does stent graft composition play a material role in the postimplantation syndrome?