Skillful anesthesia and surgical operations do not significantly increase the demands upon the heart for work. Patients who have organic heart disease but who have been able to carry on normal daily activities without symptoms referable to the heart tolerate anesthesia and operation without difficulty provided that anoxia, hemorrhage and shock are avoided. Hypertension, cardiac enlargement, valvular disease other than advanced aortic stenosis, and electrocardiographic abnormalities, per se, do not increase surgical mortality or postoperative morbidity. When symptomatic myocardial insufficiency or evidence of congestive heart failure is present, a period of preoperativre treatment with rest, digitalis, sodium restriction and mercurial diuretics is advisable. Treatment should be as thorough as possible during the interval in which the operation can be safely delayed. With adequate management, patients who have had myocardial failure can be expected to tolerate aniesthesia and surgery satisfactorily. Postoperative complications, such as pneumonia, atelectasis, thromboembolic accidents and abdominal distention, are not well borne, however, and may be responsible for a return of cardiac decompensation. Patients who have auricular fibrillation or auricular flutter should be digitalized before operation even though there have been no symptoms of impaired myocardial reserve and regardless of the ventricular rate. Surgery should be avoided if possible in persons who have severe coronary disease, aortic stenosis, coronary ostial steniosis due to syphilitic aortitis, and high grade or complete auriculoventricular block complicated by the Stokes-Adams syndrome. Spinal anesthesia should not be employed in the presence of these conditions. The decision as to the exact type of operation to be performed is seldom influenced by the existence of organic heart disease. The presence of organic heart disease is only occasionally of more than secondary importance in determining the choice of the anesthetic agent to be given by inhalation. Cyclopropane, however, should not be used. Although unimportant disturbances of cardiac rhythm occur frequently during anesthesia and operation, serious complications such as ventricular tachycardia, standstill of the heart and ventricular fibrillation are uncommon. The treatment of these conditions has been discussed. Postoperative cardiac complications are not common and are seldom responsible for death of the patient. The greatest incidence occurs in patientswhohaveseverecoronaryarterydisease. The intravenous administration of fluids which contain sodium should be avoided during operation and the postoperative period unless their use is specifically indicated.