We encountered three patients who showed ECG changes, suggesting cardiac conduction abnormality, immediately after the induction of general anesthesia with remifentanil and thiamylal. The first patient was a 42-year-old man (172cm and 75kg). The second patient was a 75-year-old woman (153 cm and 62 kg) and the last patient was 16-year-old woman (166 cm and 46 kg). Remarkable past history was not noted and pre-anesthetic evaluations including 12 lead electrocardiogram demonstrated no abnormality in all patients. Immediately after the induction of anesthesia, atrioventricular dissociation, sinus arrest and atrioventricular junctional rhythm were diagnosed by monitoring electrocardiogram, respectively. The conduction abnormalities were not followed by severe bradycardia and hypotension, and observed without drug administration. In the first and second patient, sinus rhythm returned within 15 to 20 min after the induction. The junctional rhythm in the third patient continued during the operation; however, the recovery to sinus rhythm was observed at the end of operation lasting about 1 hr. No severe adverse clinical complication was found; however, careful monitoring might be required to pre vent circulatory depression with combination of remifentanil and thiamylal.