The study enrolled 53 patients (29 males, 24 females) with respiratory mycoplasmosis aged 15-88 years. Most of them were 59 years of age and younger. In 1/3 of the patients the diseases started with symptoms of acute respiratory viral infection, in 2/3 of them--with pulmonary affection. Pneumonia was diagnosed in 50 patients (94.3%), acute bronchitis--in 3 patients. ECG changes were registered in about half of the examinees who had no cardiac complaints. 25 of them had alterations in the end part of the ventricular ECG complex; rhythm and conduction disturbances occurred rarely. Mycoplasmosis patients suffering from ischemic heart disease (IHD) had stable ECG changes while in those free of IHD the changes were short. Myocardial necrosis foci were absent. Cardiac damage comparison in patients with respiratory mycoplasmosis and in other acute respiratory infections has found that cardiovascular system suffers less in acute mycoplasmosis. These data are useful in differential diagnosis of myocardial infections.