The main difference between macrocyclic Gd-DOTA and linear Gd-DTPA complexes is the greater stability of the former which theoretically might reduce biological interactions in man. To evaluate the clinical relevance of this property, 300 unselected neurological patients were included in a randomised double-blind comparison involving five European centres, focused mainly on the tolerance of these two contrast media. Clinical tolerance was assessed immediately after the procedure and 24 h later. Adverse events were found with a similar frequency in the two groups (17.3% for Gd-DOTA and 19.3% for Gd-DTPA). Minor neurological symptoms were the most frequent (48.6%) headache being the most common (29.2% of adverse events). No difference in efficacy was found.