Abstract: Changes in the left ventricular diastolic function following coronary occlusion and the effects of hemodilution with fluorocarbon emulsion on the alterations of -dp/dt_max, -V_CE and the time constant of isovolumic pressure fall subsequent to -dp/dt_max(T) during myocardial ischemia were observed in 40 anesthetized open-chest rabbits. The animals were randomly divided into five groups, animals in group 1 were untreated during myocardial ischemia (control group) and that in group 2 and 3 were hemodiluted with dextran-40 or fluorocarbon emulsion, respectivly, at 15 min post-occlusion. Animals of the other two groups, hemodilution with dextran-40 (group 4) or fluorocarbon emulsion (group 5) were performed before coronary occlusion. It was shown that, after coronary occlusion, both -dp/dt_max and -V_CE were decreased significantly and T was prolonged obviously. At 15 min post-occlusion, -dp/dt_max -V_CE and T changed to the same extent in group 1,2 and 3. However, Their alterations were quite different in the three groups after 30 min of coronary occlution. In group 1, cardiac function was further aggrevated; in group 2, it was not worsened and in group 3, it was improved distinctly. Pre-occlusion hemodilution with fluorocarbon emulsion could also improve cardiac function following coronary occlusion. These results suggest that hemodilution with fluorocarbon emulsion has a beneficial effect on left ventricular diastolic function during myocardial ischemia.