Gadolinium (Gd)-DTPA-dimeglumine is an extracellular contrast agent (0.5 mol/L) for magnetic resonance imaging. At a dose of 0.1 mmol/kg body weight occasional slight transient elevations of serum iron and bilirubin were observed. To verify these findings, to determine time course, and to assess probability of drug relationship, a single-blind, randomized cross-over study in 12 healthy male volunteers was conducted. Either 0.25 mmol Gd-DTPA/kg body weight or the corresponding volume control 0.5 ml 0.9% saline/kg body weight were injected intravenously with an interval of one week. No relevant clinical side effects were reported or observed. Differences between the two treatments were found for serum iron, total bilirubin, and indirect bilirubin. An increase of serum iron and total bilirubin is observed at 3 to 4 hours postinjection, with a maximum at 6 to 12 hours. At 24 hours after injection all values were back to baseline range. This is a predictable side effect of no recognizable clinical consequence. The unchanged values of the intraerythrocytic enzymes and of haptoglobin indicate the minor nature of this phenomenon. Current experiences with the clinical application of Gd-DTPA at a dose of 0.1 mmol/kg body weight suggest that serum iron and bilirubin increases with that dose are less frequent and less marked than increases shown in this study at a dose of 0.25 mmol/kg body weight.