Objectives: To evaluate the potential angiographic predictors of side branch (SB) compromise after - provisional bifurcational coronary intervention in the form of main vessel stenting. Design: Prospective cohort study. Setting: Our study was conducted between June 2018 and February 2020 in the Zagazig university hospitals catheter unit. Subjects: We included 200 patients with 200 bifurcation coronary lesions who underwent provisional main vessel stenting. Interventions: Two separate cardiologists checked coronary angiography and intervention films for potential predictors of side branch (SB) compromise including the corrected bifurcat ion angle (BA) which is the sum of proximal and distal bifurcation angles. Main outcome measures: We checked all patients for SB compromise in the form of decrease in thrombolysis in myocardial infarction grade or increase in the percentage of ostial stenosis. Results: Side branch compromise occurred in 56 patients (28% of patients). Compared to the non-SB compromise group, patients in the SB compromise group had significantly narrower distal BA (P = 0.022) and narrower corrected BA (P < 0.001). Multivariate analysis demonstrated that the corrected BA was the best independent predictor of SB compromise with a best cut off value ≤ 180̊, and an area under the curve of 0.684 (P < 0.001). The JSC-TOP (Jailed SB wire, SB Stenosis percentage, Corrected BA, lesion Thrombus, distal main vessel stent Oversize, Proximal optimization technique)factor was calculated from the best predictors of SB compromise with a better area under the curve (0.867; P < 0.001). Conclusion: The corrected bifurcation angle and the JSC-TOP factor are novel predictors of SB compromise during provisional bifurcation coronary intervention. KEYWORDS: Bifurcation coronary artery disease, True bifurcation, Side branch occlusion