We analyzed the long-term influence of fixation systems on proximal aortic neck (PAN) evolution by comparing 2 late-generation endoprostheses, Endurant (Medtronic Vascular, Minneapolis, Minn) with suprarenal fixation (SRF) and Excluder (W.L Gore & Associates, Flagstaff, Ariz) with infrarenal fixation (IRF). Our retrospective observational study included consecutive patients undergoing endovascular aneurysm repair (EVAR) for aorto-iliac aneurysms (2011-2020). Primary end points: neck enlargement and freedom from significative PAN enlargement (5mm). Secondary end points: neck-related reintervention, endoleaks and graft migration. Results were reported following the Society of Vascular Surgery reporting standards. 139 patients were included (97 in SRF group and 42 in IRF group). A difference in growth at 10mm caudal to lowest renal artery at 2years follow-up was found (mean growth of 1.92±3.38mm in SRF and 0.16±6.86mm in IRF; P<0.001). A tendency to a major growth in SRF at 4years follow-up at the lowest renal artery (1.27±3.36mm vs. 0.63±2.2mm; P=0.06), 5mm distal to lowest renal artery (2.17±3.52mm vs. 0.94±2.76mm; P=0.001) and 10mm distal to lowest renal artery (2.65±3.86mm vs. 1.12±1.5mm; P<0.001) was shown. Freedom from PAN enlargement was 96.65% and 88.20% in SRF and 100% and 94.4% in IRF at 2 and 4years follow-up respectively (log rank 0.041). A greater incidence of type II endoleaks in IRF was observed (40.48% vs. 15.46%; P=0.001). Oversizing >15% showed to be a risk factor of PAN enlargement (odds ratio 6.85; 95% confident interval: 1.67-28.4; P=0.007). A small but significative percentage of patients after EVAR show a progressive PAN enlargement, being significatively greater in SRF, without increasing neck-related complications 4years after graft deployment.