A new non-ionic, dimeric contrast medium iodixanol (Nycomed AS, Norway) has a very low osmolality and is isotonic with blood. It has been compared with ioxaglate (Hexabrix, Laboratoire Guerbet, France) in a double-blind, randomized, parallel trial. The aims of the trial were to evaluate and compare the safety (vital signs, adverse events, discomfort and clinical-chemical parameters in blood and urine) and radiographic efficacy (diagnostic information and radiographic density) of iodixanol 320 mg I/ml vs ioxaglate (Hexabrix 320 mg I/ml) in coronary angiography and left ventriculography. Seventy-six patients referred for cardioangiography, two patients were withdrawn, 36 receiving iodixanol and 38 ioxaglate were included in the trial. Six patients (16%) in the iodixanol group and 16 (42%) patients in the ioxaglate group reported adverse events (P = 0.02). One serious adverse event occurred in the iodixanol group where a patient experienced transient cortical blindness and transitory global amnesia, but the patient recovered completely the day after the examination. Twenty-six patients reported injection-associated sensation of warmth in the iodixanol group versus 34 in the ioxaglate group (P = 0.06). Following contrast injection there were no differences between the groups regarding vital signs (ECG, heart rate, left ventricular pressures). Both contrast media were well tolerated by the kidneys, and on average only minor effects on clinical-chemical parameters in blood and urine were observed in the two groups. The radiographic efficacy was good in both groups.