A clinical comparison of ioxaglate and diatrizoate with regard to the cardiovascular effects following selective pulmonary angiography was performed in 20 patients with normal pulmonary arterial pressure. Ioxaglate produced a significantly less marked effect on systemic blood pressure (p less than 0.001), pulmonary arterial pressure (p less than 0.001), and heart rate (p less than 0.05-0.01), as compared with diatrizoate.