BACKGROUND: Premature coronary artery disease (CAD) is still prevalent worldwide and may differ in various ethnicities. Due to the presence of different ethnicities in Iran, the Iran-premature coronary artery disease (I-PAD) study aimed to determine the frequency of premature CAD and related risk factors based on each ethnicity.METHODS: In this multi-center case-control study, 4000 patients with premature CAD from ten different ethnicities who lived in different cities of Iran and underwent coronary angiography were enrolled (women aged ≤ 70 and men ≤ 60 years). Patients with CAD defined as obstruction equal or above 75% in at least a single coronary artery or left main ≥ 50% were included in the case group, while patients with normal coronary arteries were included in the control group. Lifestyle behaviors, cardiometabolic risk factors, anthropometric measurements, and other variables were collected. Serum, whole blood, buffy coat, plasma, urine, stool, and saliva samples were stored.RESULTS: The number of patients enrolled until April 2020 was 2071. The mean age of patients was 53.51 ± 7.52 and 934 (45.09%) of patients were women. To date, about 39.6% of the patients were normal. Also, about 26.0% were with one-vessel disease (1VD), 15.0% with two-vessel disease (2VD), and 15.2% with three-vessel disease (3VD). More than 30000 patients' biosamples from across the country have been stored.CONCLUSION: Knowing the frequency of premature CAD according to different ethnicities with major differences in their lifestyle behaviors and risk factors can assist health decision-makers. In addition, I-PAD biosamples will be an invaluable source.