Background: In patients with STEMI, culprit lesions are frequently located immediately distal to bifurcations and in proximity to major vascular curvatures. Culprit lesions in the LCA are more proximal, are closer to bifurcation branches, and result in larger infarctions and greater in-hospital mortality than culprit lesions in the RCA. Objective: The aim was to evaluate the frequency and distribution of culprit lesions in patients with ST-segment elevation acute myocardial infarction. Methods: In this prospective cohort study 222 patients with STEMI were included in the period from June 2014 to June 2019 at the cardiology department in Agouza hospital. Patients were divided into 3 groups: Group (A): includes patients with culprit lesion is in LAD Group (B):includes patients with culprit lesion is in LCX .Group (C) :includes patients with culprit lesion is in the RCA. We survey the number of culprit lesions in every 10 mms extent from ostium , bifurcation and curvature using angiography, intravascular ultrasound and instantaneous wave-free ratio IFR)) Results: Culprit lesions were within 20 mm of a bifurcation in 77% of patients and closer to the bifurcation in the LCA compared with the RCA. RCA culprit lesions, 45% were within 20 mm of a major curvature. Compared with those in the RCA, culprit lesions in the LCA were more proximally and were associated with larger myocardial infarctions. Conclusion: In patients with STEMI, culprit lesions are frequently located immediately distal to bifurcations and in proximity to major curvatures. Keywords