Reversible QRS complex changes associated with ST-segment shift during acute myocardial ischemia (AMI) have been reported sporadically in isolated cases or in small patient groups but have not been analyzed systematically in a sizable cohort of patients. During the past 4 years, a purposeful search was made for electrocardiograms with documented reversible QRS changes associated with all acute injury pattern. The measured variables included distribution of leads with ST-segment deviation and reciprocal ST-segment depression, magnitude of the ST-segment shift, amplitude and direction of the initial and terminal QRS deflections, QRS duration, QTc duration, and U wave amplitude. Reversible QRS changes encountered in 29 patients with AMI included new Q waves (n = 3), decreased Q amplitude (n = 2), QS change to qRS or qR (n = 6), disappearance of QS or Q (n = 4), increased R amplitude (n = 9), decreased R amplitude (n = 6), increased S amplitude by more than 75% (n = 18), and increased QRS duration (n = 4). Changes in the initial configuration were present in 24 of the 29 patients. Reversible changes of the terminal QRS portion occurred in all 29 patients, and reversible changes of the initial QRS portion occurred in 23 (79%), whereas QRS duration increased in 4 patients. Reversible QRS changes during AMI are attributed to passive pull by the ST-segment shift and intraventricular conduction disturbance.