Electrocardiographic abnormalities are common after transthoracic electrical cardioversion (ECV), which may indicate DC shock-induced transient cardiac dysfunction or myocardial injury. The incidence and clinical significance of post-ECV Brugada-typed or saddle-back (nonspecific) type of ST segment elevations (STE) remains to be determined. We prospectively enrolled 96 subjects (M:F=79:17, mean age, 57.4짹9.9 yrs old) underwent transthoracic ECV with biphasic wave forms for paroxysmal atrial fibrillation (n=12), persistent AF (n=38), permanent AF (n=44), and atrial flutter (n=2). The transient STE of either coved type or nonspecific STE at least 0.1 mV on V1-3 ECG within 10 seconds after ECV and later follow-up ECG were evaluated. Amount of energy, last delivered energy, number of shocks, and underlying diseases were compared between group with and without STE. Twelve (12.5%) revealed typical Brugada-typed STE only on V1 and fifty-three (55.2%) showed nonspecific STE on V1-3. STE in all patients returned to baseline during follow-up of 26.8짹 26.2 days. The total amount and last delivered energy were not different between group with two patterns of STE and those without STE (193짹220 J vs. 115짹88 J and 94짹54 J vs. 82짹25 J, respectively). However, patients who had transient STE either Brugada-typed or nonspecific had a higher number of shock compared to those who did not (2.7짹0.7 vs 1.6짹0.6, P=0.03). STE was not associated with underlying diseases. No clinical (ventricular arrhythmias or ischemia) events were observed in all patients during follow-up. Conclusion: Transient Brugada-typed or nonspecific STE was not uncommon after transthoracic ECV. Number of DC shock was associated with occurrence of STE, however, it does not indicate further clinical events.