Iomeprol is a new triiodinated, nonionic radiographic contrast agent prepared for injection at a number of concentrations (150, 200, 250, 300, 350 and 400 mgI/ml), each of which has osmolality and viscosity properties that are more favourable than other current nonionic monomers at the same iodine concentrations. Pharmaco-toxicological studies in animals have demonstrated that the molecular toxicity of iomeprol is very low. Intensive monitoring of vital, electro-physiological, and biochemical parameters in clinical studies have shown that iomeprol does not have clinically significant effects on the more important body systems and functions. Out of 7799 patients to whom iomeprol was administered, adverse events were observed in only 437 (5.6%). Of these events, the majority were rated as mild. In double-blind controlled clinical studies the contrast efficacy of iomeprol was shown to be as good as that of reference contrast media. The good efficacy was confirmed in a very large number of uncontrolled studies.