The inflammatory response--mediated by activated neutrophils--is assumed to play an important role in the pathogenesis of reperfusion injury. This study investigated whether extravascular myocardial neutrophil accumulation between 3 and 72 h of reperfusion affects infarct size in porcine hearts. The left anterior descending coronary artery was ligated distally in 24 pigs for 45 min and reperfused for 3 h (n = 8), 24 h (n = 8), or 72 h (n = 8). Infarct size and extravascular myocardial accumulation of neutrophils was evaluated at the end of the experiments. Global hemodynamic characteristics were comparable for the three groups both before and during ischemia. Neutrophil count/mm2 reperfused myocardium increased substantially from 4 +/- 2 (3 h of reperfusion) to 129 +/- 70 (24 h of reperfusion, p < 0.001). After 3 d of reperfusion, the neutrophil count had decreased to 10 +/- 7. The invasion of neutrophils between 3 and 24 h of reperfusion did not significantly affect the extent of myocardial necrosis. Infarct sizes after 3 h (62.6 +/- 20%), 24 h (71.8 +/- 13%), and 72 h of reperfusion (67.6 +/- 18%) did not differ significantly. This finding does not suggest that a significant amount of myocytes are destroyed by extravasated neutrophils between 3 and 72 h of reperfusion.