Serial electrocardiograms were taken in 46 Hajj Pilgrims suffering from heat stroke immediately after cooling 12 and 24 h later. The collected data were analyzed and revealed that a statistically significant number of patients with heat stroke had sinus tachycardia (43 percent, p < 0.05), conduction defect (22 percent, p < 0.046), prolonged Q-T interval (61 percent, p < 0.007), diffuse nonspecific ST-T changes (26 percent, p < 0.036), and ST-T changes (localized to the ECG leads confirming to a territory of coronary artery) consistent with myocardial ischemia (21 percent, p < 0.02). Although adverse effects of heat stroke on the heart are multifactorial, the above data indicate that heat stroke predisposes to certain risk of myocardial ischemia and conduction disturbances. This may reflect the true cardiovascular status of these heat stroke victims.