Pneumonia is the most common clinical feature of Legionnaire's disease. Its mostly seen complications are pericarditis, myocarditis, and endocarditis. A 27-year-old man with Legionella pneumonia, was treated and discharged from our hospital without any problem. However, on the 16th day of erythromycin treatment, myocarditis and then a thrombus in the left ventricle developed. The patient died due to cerebral emboli.