Objective: A novel application of microdialysis was studied, where myocardial outflow of aminoacids and purines were monitored by intravasal microdialysis in the myocardial venous outflow during ischemia and reperfusion. Methods: Microdialysis catheters were introduced into the great cardiac vein, pulmonary artery and external jugular vein in 20 anaesthetised pigs. The left anterior descending artery was occluded in four groups of pigs for 0 min, 10 min, 15 min, and 60 min, respectively. Ischemia was followed by 120 min of reperfusion. Microdialysis samples were analysed for taurine, aspartate, glutamate, hypoxanthine, inosine and guanosine. Results: Myocardial infarction developed when ischemia exceeded 10 min. Taurine, aspartate, inosine and guanosine increased early in great cardiac vein during ischemia. We found the outflow patterns of aminoacids and purines to be graded in response to different lengths of ischemia. Conclusion: In this study we have demonstrated a graded outflow of aminoacids and purines in response to ischemia and a positive correlation between infact size and myocardial outflow of aminoacids and purines. This could be of value in a clinical setting to quantify the extent of myocardial damage.