Objective: To study the overall causes, perioperative mortality, post operative complications, prognosis, outcome and follow up in a young adult present with coronary artery disease under going coronary artery bypass in our institute. Methods: Asum of 56 patient who are 40 years and less then 40 years who underwent coronary artery bypass surgery between January 2017 to December 2022 who's clinical case history, coronary angiography, pre operative and post operative echo cardiography, operative notes, post operative notes, outpatient follow up are collected from our computer stored data and from medical record department in our college and from Tamilnadu chief minister comprehensive health insurance scheme institutional Web site data base Results: Out of 56 patient,8 Female(14.3%) and 48 Male(85.7%),mean age 37.1 years (range 32 – 40 years),Diabetic 39 Patient (62.5%),Hypertensive 21 patient (37.5%) 7 / 8 women(87.5%) diabetic ,3/8 women both diabetic and hypertensive. Out of 48 male 47(97.9%) chronic smoker, 45 (93.8%) chronic alcoholic,44 (91.6%) both alcoholic and smoke , no women in this study neither alcoholic or smoker, 3patient (5.35%) hyperlipidaemia, 2 patient (3.57%) hypothyroidism all 2/8 (25%) are female,2 patient on haemodialysis for kidney disease, 1patient with bilateral renal artery stenosis, 1 patient with right innominate, right subclavian, bilateral carotid stenosis. Left ventricular function was impaired with ejection fraction average 46% (range 30% - 55%). 1 patient with ventricular septal rupture.2 patient with post coronary stent, The indication for surgery was triple vessel disease in 30 patient(53.57%) ,double vessel disease in 20 patient(35.7%),single vessel disease in 1 patient, single vessel disease with ventricular septal rupture in 1 patient, left main coronary artery stenosis in 4 patient(7%). Surgical procedure Off pump coronary artery bypass surgery in 51 patient(91%), On pump beating heart coronary artery bypass surgery in 2 patient (3.57%),On pump arrested heart coronary artery bypass surgery in 3 patient(5.35%). A total of 132 grafts were constructed(mean 2.4 grafts per patient),35 (27%) of them being arterial only left internal mammary artery harvested and other grafts were great saphenous vein. Post operative average ventilation time18hrs (range 18hrs to 24hrs), There were 5(8.9%)hospital death and 5(8.9%) late death in follow up, total 10 (17.8%) death till now. Conclusion: Most common cause for young coronary artery disease from our clinical history is found to be early onset diabetic mellitus and from our personal history chronic smoking and chronic alcoholism, intra operative mortality and morbidity is high in patient present with severe left ventricular dysfunction, coronary artery diseases induced complication and additional comorbidity, however most of patient recovered from post operative cardiovascular lethal or morbid event and on regular clinical follow up