Introduction: Following our previous published 1 parallel-stent in-vitro study, the aim of this study is again to identify which endograft-parallel stent combination, and to what degree of oversizing, may result in the most adequate fit in a juxtarenal abdominal aneurysmal neck, but when using a double or triple parallel-stent (chimneys) technique. Methods: In-vitro silicon aneurysmal neck models of different diameters, with two and three side-branches (simulating both renal and superior mesenteric arteries), were constructed. Two different endografts (three diameters each) with two or three parallel-stents (of 6e6 mm, or 6e 6e8 mm) were tested (MedtroniceEndurant endograft with balloonexpandable BentleyeBeGraft, and GoreeExcluder endoprosthesis with selfexpanding GoreeViabahn), applying three endograft-oversizing degrees (15%, 30% and 40%). After remodeling using the kissing-balloon technique at 37 C, the 36 endograft-stent-oversizing combinations were scanned by computed tomography (CT). The size of the results in gutters, parallel-stent compression and main stentgraft infolding were recorded. Results: Increasing oversizing (15%, 30% and 40%) showed a nonsignificant tendency towards smaller gutters and similar parallel-stent compression, but it significantly increased infolding, mainly for Excludere Viabahn combination, and more in 3 parallel-stent models (0e67e100% and 0e0e100%, P ¼ 0.043 and 0.011 for ExcludereViabahn in 3 and 2 parallel-stent models, and 0e0e67% and 0e0e33%, P ¼ 0. 076 and 0.325 for EnduranteBeGraft). ExcludereViabahn combination showed significant lower gutters (8.2, 22.6 mm 2 , P ¼ 0.002 and 14.4, 23.3 mm 2 , P ¼ 0.009 for 2 and 3 parallel-stents), but with higher stent compression (18%, 2%, P < 0.001and 15%, 2%, P ¼ 0.007) than EnduranteBeGraft combinations for all oversizings. Conclusion: When using the parallel-stent technique during EVAR for 2 and 3 parallel-stents, this in-vitro study shows that increasing endograft oversizing is related to a tendency to smaller gutters and not increasing stent compression. However, infolding appears in most 40% oversized models, and is more frequent with 3 than 2 parallel-stents, and with ExcludereViabahn than EnduranteBeGraft combinations; thus, 30% oversizing is the most optimal oversizing (and only 15% for ExcludereViabahn with 3 parallel stents). Lower gutters, but higher stent compression, are achieved with ExcludereViabahn than with EnduranteBeGraft combinations.