Twenty cases of heat stroke in dogs, observed during hot/hot humid months, were investigated for myocardial damage, if any, employing electrocardiography and estimation of cardiac troponin-I. Heat stroke in dogs was clinically characterized by sudden onset of hyperthermia (temperature > 107.0 °F) during hot/hot humid months, impaired consciousness, severe panting and associated symptoms. Their haemogram reflected thrombocytopenia and increased levels of haemoglobin, packed cell volume, total erythrocytes and total leucocytes. Electrocardiographic abnormalities such as sinus tachycardia (heart rate 240 to 320 beats per minutes), ventricular premature complexes (8-10 per minute), ventricular tachycardia (ventricular rate 180-220), ventricular fibrillations, and 3rd degree heart block associated with increased level of cardiac troponin- I (mean 3.34±1.11 ng/ml) suggested myocardial damage in the dogs with heat stroke.