Background Emergent complex aortic diseases are challenging to treat. When off-the-shelf grafts are unsuitable and patients are unfit for open repair the remaining option is often some type of physician modified graft. One type of modification is the In-situ laser fenestration (ISLF), where aortic side branches are covered and flow restored with in-situ fenestration of the stent graft. The aim of this presentation is to discuss evidence and technical details of the procedure. Methods Resume of published reports on ISLF technique. The ISLF technique can also be facilitated by an off-the shelf, single SMA-fenestrated device – then mesenteric ischemia is avoided and renal ischemia time shortened. Features of an optimized design of such an endograft suitable for >90% of juxta- and pararenal AAAs is demonstrated. Also a clinical report of ISLF of visceral aortic stent-grafts 2018-2023 in three aortic centers: In total 65 ISLFs were performed in 34 patients. The procedure was acute in 79%, and 35% were ruptures. Four patients (12%) died within 30 days, all presented with a rupture. Technical success was achieved in 61/65 ISLF (94%). Median follow up was 16 months. Cumulative survival at six months, one year and two years was 88%, 80% and 72%. Conclusion ISLF is a useful tool for emergent endovascular procedures in complex anatomies when off the shelf grafts and open surgery is not feasible.