OBJECTIVE The aim of this phase-III clinical trial was prospectively to evaluate the clinical safety and diagnostic efficacy as well as the effects on laboratory and electrocardiographic parameters of new iodinated, nonionic, low-osmolality contrast medium, iobitridol(Xenetix 350) during coronary angiography in adults in comparison to an iodinated, nonionic, low-osmolality reference product, iohexol (Omnipaque). METHODS This 2-center, comparative, randomized, double-blind trial involved 90 patients, 46 receiving iobitridol and 44 iohexol. Clinical safety was evaluated by recording the adverse events observed during investigation and by the patient's assessments. Electrocardiographic effects on laboratory parameters were evaluated as well as diagnostic efficacy. RESULTS The age, sex, presence of risk factors and clinical picture ( unstable angina, postinfarction) were not significantly different between the 2 treatment groups. The incidence of significant coronary lesions (stenosis 50%) was also not significantly different between the 2 treatment groups. Clinical safety was good in both groups. Four patients experienced an adverse event, 2 in each group. In the iobitridol group, one patient had an episode of hypertension, followed by hypertension and prolonged chest pain was observed and one patient had sinus tachycardia. In the iohexel group, chest pain was observed in one patient and nausea in another. ECG safety was good in both groups. Transient excitability disorders were observed in 10 and 6 patients, respectively. Moderate conduction abnormalities were noted in one patient in each group and repolarization abnormalities in 10 and 8 cases, respectively. Safety in laboratory parameters was good with no significant changes in either. Diagnostic efficacy was good to excellent in all patients. CONCLUSIONS Diagnostic efficacy and safety of iobitridol 350 in terms of effects on clinical, laboratory and electrocardiographic parameters were comparable to those of the nonionic reference product.