Background: Negative dromotropic agent is considered as an important cause of symptomatic atrioventricular block (AVB). However, it is little known about the natural history and prognosis of patients with drug-related AV block (DR-AVB). We, therefore, compared the clinical and electrocardigraphic features in patients with DR-AVB underwenting with not underwenting implantation of permanent pacemaker (PM) after discontinuation of the culprit drug. Methods: In 190 patients with clinically documented AVB, 30 patients who had DR-AVB were assessed. DR-AVB was classified into 3 groups; 1) DR-AVB caused by drug (drug-induced, group I, n=9), 2) DR-AVB not cuased by drug (drug-provoked, group II, n=11), and 3) DR-AVB undetermined relation (drug-associated, group III, n=10). Results: In all patient with group II and III AVB, permanent PM was implanted. In contrast, in group I, AVB was reevaluated after at least 6 months of washout period. 7 of them (78%) completely recovered, but 2 patients (22%) who persistently revealed complete AVB were implanted PM. Among various ECG parameters, QRS width was significantly longer in group III than other group (p=0.018 vs group I; p=0.027 vs group II). Conclusion: After drug-induced AV block resolved, patients should be closely monitored for recurrence of AV block while the medications are discontinued. Also, longer QRS width during AVB may indicates pure drug-induced AVB less likely.