The pharmacodynamic effects of iomeprol on the cardiovascular, central nervous, coagulation, and complement systems and on renal and thyroid functions using a wide range of intravenous and intraarterial radiological procedures were evaluated in Phase I, Phase II and Phase III clinical studies. The pharmacokinetics and metabolism of iomeprol were studied in healthy volunteers. Iomeprol 350 and 400 mgI/ml at doses ranging from 100 to 300 ml did not cause any significant changes of the basal haemodynamic parameters when used in CT of the chest and upper abdomen. No significant alterations of haemodynamic and ECG parameters were seen in patients who underwent cardiac-angiography or coronary angiography with iomeprol 400 mgI/ml. Intensive monitoring of haemodynamic and EEG parameters in patients undergoing conventional cerebral angiography with iomeprol 300 mgI/ml confirmed good toleration by the CNS. Neither renal and thyroid functions nor the coagulation and complement systems were significantly affected by iomeprol. Iomeprol was not metabolised and did not bind to plasma proteins. In healthy volunteers it was excreted almost exclusively by renal glomerular filtration (about 90% of the injected dose after 24 h). The pharmacokinetic behaviour of iomeprol was very similar to the behaviour of other nonionic, monomeric agents.