Gadodiamide injection is a new nonionic paramagnetic, extracellular contrast medium. Its safety at a dose of 0.1 mmol/kg body weight was evaluated in a large European multicentre trial on adults referred for contrast-enhanced MRI of the central nervous system. Safety analysis was performed on 2102 patients, in whom adverse events during and up to 24 h after injection were recorded. Adverse events related or possibly related to gadodiamide injection were observed in 102 patients. Injection-associated reactions classified as discomfort (sensation of heat or coldness, pain or pressure at the injection site) occurred in 37 patients (1.8%) and other adverse events (e.g. headache, nausea) were observed in 65 patients (3.1%). No serious adverse event was reported. Efficacy analysis, performed on 2273 patients, and based on comparison of T1- and T2-weighted images before and T1-weighted images after injection showed that more diagnostic information was obtained after gadodiamide injection in 1424 (62.6%) patients: management of 386 (17.0%) patients was affected by the new information given and that a new diagnosis was made in 755 (33.3%) patients. Gadodiamide injection was shown to be safe and well tolerated. It represents a nonionic alternative to the current products for MRI of the central nervous system.