Purpose: We aimed to evaluate the use of APACHE score in predicting mortality in open and endovascular TAA and AAA repair. Methodology: We performed a retrospective cohort study, in a single-centre tertiary hospital, on all patients who underwent surgery for either TAAs or AAAs between January 2014 – December 2022 (n=424). Of these, patients who required admission to ICU post-operatively were included, with APACHE scores collected prospectively. Outcomes included ICU and total length of stay, as well as mortality. Receiver operator characteristics (ROC) is used to evaluate the use of APACHE on inpatient mortality and long-term 5-year mortality. Results: 72.0% (n=203) had elective AAA, 18.4% (n=52) ruptured AAA, 7.1% (n=20) elective TAA and 2.5% (n=7) ruptured TAA. 68.8% (n=194) underwent endovascular repair and 31.2% (n=88) open. Mean age was 74.1±8.66 years with male preponderance of 82.6% (n=233). ROC demonstrates improved area under curve (AUC) for inpatient mortality (0.927), compared to 5- year mortality (0.594), open (0.982) compared to endovascular (0.819) repair, and elective (0.990) compared to rupture (0.861). Conclusion: APACHE score is a predictor of inpatient mortality after TAA and AAA repairs, with improved predictions in open compared to endovascular repair, and in elective surgeries compared to ruptures. This may highlight reduced physiological derangements from endovascular approaches. References 1) Vos CG, de Vries J-PPM, Werson DAB, et al. Evaluation of five different aneurysm scoring systems to predict mortality in ruptured abdominal aortic aneurysm patients. Journal of Vascular Surgery 2016; 64: 1609-1616. DOI: 10.1016/j.jvs.2016.05.099. 2) Kabbani LS, Escobar GA, Knipp B, et al. APACHE III score on ICU admission predicts hospital mortality after open thoracoabdominal and open abdominal aortic aneurysm repair. A n n a l s o f v a s c u l a r s u r g e r y 2010; 24: 1060-1067. DOI: 10.1016/j.avsg.2010.07.011.