Case 1: a 40-year-old man was admitted to our hospital with progressively worsening post myocardial infarction angina. Cardiac catheterisation was performed, which showed total occlusion of the left anterior descending artery (LAD) and the left circumflex artery (LCX) was not visualised. The right coronary artery (RCA) was a large artery supplying the left ventricular inferior and posterolateral walls and filling the LAD artery in retrograde. The patient was referred for coronary artery bypass grafting. Peroperative findings confirmed the angiographic evidence of congenitally absent LCX artery. Case 2: a 39-year-old man with a family history of premature coronary artery disease underwent coronary angiography for the work-up of chest pain. A coronary angiogram showed normal LAD artery and absence of left circumflex system. The RCA was superdominant. An aortogram confirmed no anomalous origin and true absence of LCX artery.