Gd-DTPA is the first paramagnetic contrast agent approved for clinical use in cranial and spinal MRI in the F.R.G., U.S.A., Japan and several other countries. After submission 13,439 patients were enrolled in standardized protocolled clinical trials. The observed adverse drug reactions (ADRs) after i.v. injection of Gd-DTPA were comparable to those after administration of iodinated non-ionic roentgen contrast media (CM). However, the overall incidence of ADRs after intravenous injection of 0.1 or 0.2 mmol/kg body weight Gd-DTPA was found to be even lower. Adverse events were observed in only 1.46% of the patients - or 1.14% if localized warmth is excluded. None of them was critical. There was no correlation between patient age and the incidence of ADRs. In patients with a known history of allergy the incidence of ADRs was increased by a factor 3-4, which is still lower than the incidence reported after intravenous administration of iodinated non-ionic roentgen CM to patients without known allergy. Good renal tolerance was seen in all patients, irrespective of pre-existing renal impairment. Fast bolus injections of Gd-DTPA were tolerated without added risk. The favorable safety profile is also reflected in the post marketing surveillance reports since Gd-DTPA became available as a commercial drug.