Background: Cardiovascular disease remains the most common cause of death and disability in developed countries (1). According to a World Health Organization report published in 2012, around 7.4 million deaths occurred from CHD globally, accounting for 42% of cardiovascular-related deaths and 13% of worldwide death (2). A reliable method of risk assessment for major adverse cardiac events (MACE) during the treatment of acute coronary syndrome (ACS) is needed due to differences in clinical appearance and mortality in patients with this condition to Planning early treatment, discharge, and rehabilitation for ASC patients, conducting research following ACS, and accelerate the final treatment decision all benefit from the application of risk stratification (3,4) Aim: To determine the predictive accuracies of the GRACE risk score, CADILLAC, TIMI risk index and Killip class for patients that been diagnosis as Acute Coronary Syndrome. And find out which of them is the most accurate between them Methods: This single-center retrospective study involved 88 patients with acute coronary syndrome (ACS) who was admitted in King Faisal Medical Complex in Taif, Makkah, in the period from May 2019 to November 2021. The GRACE, TIMI, and Killip class scores were compared for their predictive ability. Results: A total of 88 patients [65 men (73.9%) and 23 women (26.1%), with the mean age (±standard deviation, SD) of 60.3±12.9 years] were enrolled in this study. There were 59 NSTEMI/UA and 29 STEMI patients in our study. There were significant differences regarding patient age (p<0.001), TRI (p<0.001), CADILLAC score (p<0.001) and GRACE score (p<0.001) in all patients between the low-, intermediate-, and high-risk groups. The area under the ROC curves for TRI was 0.954 (95% CI: 0.901-1.000, p=0.001) in the prediction of the severity of CAD (GRS >140) in patients with ACS. And ROC curves for CADILLAC was 0.859 (95% CI: 0.767-950, p=0.001) in the prediction of the severity of CAD (GRS >140) in patients with ACS. Conclusions: Our study is significant since it is the first in the field of literature to compare GRS, TRI and CADILLAC and to investigate how they relate to GRS were evaluated in the same patient population. In this study, in this research, we believe that information regarding patient short- and long-term mortality as well as information about the severity and extent of CAD may be obtained from the calculated of GRS or TRI and CADILLAC of patients who are admitted to the emergency department with ACS.