Objectives: Several epidemiologic surveillance studies have recorded adverse drug reactions to radiocontrast agents.We aimed to investigate the incidence and management of acute adverse reactions(AARs)to Ultravist(R)-370 and Isovue(R)-370 in patients who underwent contrast-enhanced computed tomography(CT)scanning.Materials and Methods: Data from 137,473 patients were analyzed.They had undergone enhanced CT scanning with intravenous injection of Ultravist(R)-370 or Isovue(R)-370 during the period of January 1,2006 to December 31,2012.We compared the incidence of AARs between Ultravist(R)-370 and Isovue(R)-370.Results: Four hundred and twenty-eight(0.31%)patients experienced AARs,which included 330(0.24%)patients with mild AARs,82(0.06%)patients with moderate AARs,and 16(0.01%)patients with severe AARs.The incidence of AARs was higher with Ultravist(R)-370 than with Isovue(R)-370(0.38%vs.0.24%,P < 0.001),but only for mild AARs(0.32%vs.0.16%,P < 0.001).Analyses on risk factors indicated that female patients(n = 221,0.43%,P < 0.001),emergency patients(n = 11,0.51%,P < 0.001),elderly patients aged 50–60 years(n = 135,0.43%,P < 0.001),and patients who underwent coronary computed tomography angiography(CTA)(n = 55,0.51%,P < 0.001)had a higher risk of AARs.Cutaneous manifestations(50.52%)— especially rash(59.74%)—were the most frequent mild AAR.Cardiovascular manifestations accounted for most moderate and severe AARs(62.91%and 48.28%,respectively).After proper management,the symptoms and signs of 96.5%of the AARs resolved within 24 h without sequelae.Conclusions: Ultravist(R)-370 and Isovue(R)-370 are safe for patients undergoing enhanced CT scanning.The incidence of AARs is higher with Ultravist(R)-370 than with Isovue(R)-370,but this difference is limited only to the mild AARs.The incidence of AARs could be affected by multiple factors.