PURPOSE: To assess changes in the electrocardiogram (ECG) associated with intraoperative infusion of adenosine in patients undergoing open abdominal gynecological surgery. METHODS: One hundred and sixty-six patients undergoing gynecological surgery were randomly assigned to receive one of four doses of adenosine infusion (25, 50, 100, or 200 μg/kg/min) or matching placebo. Study drug administration was started at skin incision and discontinued at end of surgery. A standardized general anesthetic regimen was used and adjusted based on hemodynamic and bispectral index values. Heart rate and rhythm variables, and PR, QRS, QT, and QTc intervals were recorded from 12-lead ECGs before anesthesia and immediately after patient arrival in the postanesthesia care unit. In addition, a rhythm strip was obtained during administration of the loading dose of the study drug. ECG variables were compared within and between groups. Incidence of ECG and hemodynamic abnormalities was recorded. RESULTS: One hundred and fifty-one subjects had a full set of electrocardiographic data: placebo (n = 38), group adenosine 25 μg/kg/min (n = 31), group adenosine 50 μg/kg/min (n = 29), group adenosine 100 μg/kg/min (n = 28), and group adenosine 200 μg/kg/min (n = 25). Statistically significant postoperative QTc prolongation was observed in all study groups when compared with baseline except for the adenosine 200 μg/kg/min group. However, these changes from baseline were not different among the groups. There were also no significant differences in PR, QRS, and QT intervals between the treatment groups. CONCLUSION: There was no difference in QTc prolongation following intraoperative administration of adenosine infusion compared with placebo during isoflurane general anesthesia. However, QTc prolongation is common following general anesthesia.