Rapid intravenous injections of contrast media are used for angiocardiography, intravenous digital subtraction angiography (DSA), and rapid scan computed tomography procedures. These rapid intravenous injections have been shown to produce significant hemodynamic changes that appear related to contrast media osmolality. In this study the systemic responses to 2-second injections at a dose of 1.5 mL/kg were compared for a new nonionic agent, ioxilan (350 mgI/mL), and for iohexol (350 mgI/mL), meglumine/sodium diatrizoate (370 mgI/mL), and saline. Ioxilan has a lower osmolality and viscosity than iohexol and is formulated with a 3 mM sodium citrate as a buffer and anticoagulant. All of the test solutions produced statistically significant changes in arterial pressure and respiratory rate (P less than .05, Student's t-test). The decrease in arterial pressure seen with diatrizoate (20.1%) was significantly greater than the decrease seen with either ioxilan (10.2%) or iohexol (10.2%). All of the responses observed were transient and would not be of clinical concern in a healthy patient. Ioxilan, which contains the calcium binding agent, sodium citrate, and iohexol appear to cause less systemic effects then diatrizoate.