We compared electrocardiographic abnormalities and plasma norepinephrine concentrations in 40 patients with subarachnoid hemorrhage within the first 24 hours, at 72 hours, and after 1 week. In 20 patients with high plasma norepinephrine concentrations within the first 24 hours, sinus tachycardia (p < 0.02) and negative T waves (p < 0.01) were more frequent than in the 20 patients with normal plasma norepinephrine concentrations. After 72 hours, only sinus tachycardia (p < 0.03) was found with increased frequency in the 26 patients with high plasma norepinephrine concentrations. Although 24 patients had high plasma norepinephrine concentrations after 1 week, we found no differences in the frequency of electrocardiographic abnormalities compared to patients with normal plasma norepinephrine. However, QT(c) prolongation, U waves, ST depression, and arrhythmias were found with similar frequency in patients with both high and normal plasma norepinephrine concentrations. We conclude that, with the exception of sinus tachycardia and negative T waves, electrocardiographic changes in patients with subarachnoid hemorrhage do not depend on elevated plasma norepinephrine concentrations.