The posterior descending artery (PDA) arises from the right coronary artery (RCA) in approximately 85% of people; only in from 10 to 15% does it arise from the circumflex artery. We report an unusual case of origin of the PDA from a branch of the left anterior descending artery (LAD). The PDA passed through the interventricular septum before it reached the posterior interventricular groove.