Background: In patients with ST-segment elevation myocardial infarction (STEMI), primary percutaneous coronary intervention (PCI) tries to reestablish coronary flow and ensure effective cardiac reperfusion. An independent predictor of no-reflow is a large thrombus load. Objective: This investigation sought to determine if the red cell distribution width (RDW) and neutrophil-lymphocyte ratio (NLR) were reliable indicators of excessive thrombus load on coronary angiography. Patients and methods: Two-hundred patients, with STEMI managed by primary PCI within 12 hours from chest pain onset, were divided into group A with high thrombus burden (Thrombolysis in myocardial infarction (TIMI) thrombus grade 4-5) and group B with low thrombus burden (TIMI thrombus grade 1-3).  Results: One-hundred and seventeen patients (58.5%) had a high thrombus burden (group A). They had more mean number of cardiovascular disease (CVD) risk factors (2.4 ±0.99 versus 2.06 ±1.06, p=0.02), longer pain to balloon time (PTB) (151.28 ±42.05 versus116.99 ±43.16 minutes, p < 0.001), higher mean Killip class (1.49±0.73 versus 1.28±0.6, p=0.03), higher RDW (18.99±1.55 versus 14.03±1.52, p < 0.001), and higher NLR (5.93±1.39 versus 4.08±0.93 p < 0.001) compared to group B. Independent predictors of high thrombus burden were RDW (OR: 4.06, p < 0.001), NLR (OR: 1.35, p= 0.04), number of CVD risk factors (OR: 1.62, p= 0.01), and PTB time (OR: 1.02, p < 0.001). Cut-off values to predict high thrombus burden were 16% for RDW and 4.55 for NLR.  Conclusions: Rapid identification of RDW more than 16% or NLR more than 4.55, could predict a high thrombus burden.