To assess the value of the paramagnetic contrast agent Gadolinium (Gd)-DTPA in Magnetic Resonance Imaging (MRI) of acute myocardial infarction (AMI), we studied 20 patients with a first AMI by ECG-gated MRI before and after intravenous administration of 0.15mmol/kg Gd-DTPA. The MRI studies were performed after a mean of 98 hours (range 15-241) after the acute onset of AMI. Spin-echo measurements (TE 30 msec) were made using a Philips Gyroscan (0.5 Tesla). After performing the baseline MRI scans, the MRI procedure was repeated every 10 minutes for up to 40 minutes following injection of Gd-DTPA. In 18 (90%) patients contrast enhancement in the infarcted myocardial areas was observed after Gd-DTPA. In these patients intensity versus region curves, derived from 9 to 11 adjacent myocardial regions of interest, showed increased signal intensities in the infarcted areas after administration of Gd-DTPA. The precontrast signal intensity ratio between infarcted and normal myocardium was 1.14±0.15 (mean±SD); the postcontrast ratios at 10 minutes were 1.41±0.21 (P <0.05), at 20 minutes 1.61±0.19 (P <0.01), at 30 minutes 1.43±0.20 (P < 0.05), and at 40 minutes 1.33±0.20 (P=NS). It is concluded that MRI using the contrast agent Gd-DTPA significantly improves the visualization and detection of infarcted myocardial areas in patients with AMI and that optimal contrast enhancement is obtained 20 minutes after administration of Gd-DTPA.