The hyperosmolality of current ionic angiographic media gives rise to several adverse effects. Use of the first low-osmolality medium, metrizamide (Amipaque), has been inhibited by expense and by the necessity for prior mixing into solution. Hexabrix is the first of such media to be available in stable solution, and its use in angiocardiography is reported, in direct comparison with Urografin, Triosil, Cardio-Conray, and metrizamide. The low osmolality media cause significantly less discomfort than ionic media, and are better tolerated in paediatric angiocardiography. In coronary angiography Hexabrix causes comparable T wave change to Urografin and more than Triosil or metrizamide, but tends to have less effect on heart rate. The risk of exacerbating pulmonary arterial hypertension in right heart angiography appears to be reduced.