A 61-year-old asymptomatic male patient was evaluated before abdominal surgery. He has a history of septal myectomy in 1969 and an episode of atrial flutter in 1983. On auscultation an atypical murmur was heard. By transthoracic echocardiography the diagnosis was made of a coronary artery fistula after septal myectomy. We discuss the prevalence, diagnosis and natural history of coronary artery fistulas. In our patient we followed a conservative strategy.