SUMMARYHexabrix, a dimeric intravascular medium, has an osmolality which is similar to that of nonionic contrast agents and lower than conventional monomelic media. The degree of reactive vasodilatation on aortic injection is such that the sensation of heat in the legs is usually moderate in severity while the incidence of pain is extremely low. The fall in blood pressure and rise in pulse rate are similar to those for metrizamide and less than for other contrast media. The radiographic quality of the angiograms was consistently high.