To evaluate the myocardial hemodynamic effects of a new iso-osmotic contrast agent (Hexabrix 160: H 16) a randomized cross-over study was performed comparing Hexabrix 160 with Sodium Meglumine diatrizoate (Radioselectan 76: R 76) in 20 patients with ischemic heart disease. H 16 produced substantially smaller (p less than 0.001) increases in heart rate (68 +/- 11 to 73 +/- 12) than R 76 (69 +/- 12 to 88 +/- 15) and smaller decreases in left systolic ventricular pressure (131 +/- 15 to 128 +/- mmHg) than R 76 (132 +/- 14 to 94 +/- 15 mmHg). Both contrast media resulted in an increase in contractility beginning three to five seconds after the onset of the injection and reached its maximum at 45 seconds. However the increases in contractility was smaller with H 16 than R 76: H 16 caused a significantly smaller (p less than 0.01) increases in V max. (0.1 CIRC/s) than R 76 (0.35 CIR/s). The hemodynamic effects of H 16 were probably in relation with the Frank-starling mechanism. The lowest variation of preload observed (left ventricle end-diastolic pressure: 12 +/- 4 to 14 +/- 5 mmHg) showed that this contrast medium appeared to behave like isotonic serum. These results suggest that H 16 may preferable for digital left ventriculography.