The time course of endothelial P-selectin, ICAM-1, and E-selectin expression was studied in a feline model of myocardial ischemia and reperfusion. Cats were subjected to 90 min of myocardial ischemia followed by 0, 10, 20, 60, 150, or 270 min of reperfusion. At the end of reperfusion, the coronary vasculature was examined immunohistochemically to localize monoclonal antibodies (mAbs) PB1.3, RR1/1, and Cyl787 directed against P-selectin, ICAM-1, and E-selectin, respectively. Immuno-histochemical localization for P-selectin, recognized by mAb PB1.3, was maximally expressed 20 min after reperfusion in 60 ± 6% of coronary venules (P < 0.05 compared to non-reperfused controls), and covered 59 ± 3% of the endothelial cell perimeter of immunostained coronary venules. Immunolocalization of mAb PB1.3 gradually declined at 60, 150, and 270 min of reperfusion. Immunohistochemical localization of mAb RR1/1 (anti-ICAM-1) in endothelial cells of coronary venules was observed to a modest extent in non-ischemic myocardium and at 10, 20, and 60 min of reperfusion, but was significantly increased following 150 and 270 min of reperfusion (P < 0.05 compared non-reperfused controls). At 270 min post-reperfusion, mAb RR1/1 was seen in 50 ± 4% of coronary venules. Endothelial immunolocalization of mAb Cyl787 (anti-E-selectin) was only observed in 13 ± 1 and 14 ± 3% of coronary venules after 150 and 270 min of reperfusion, respectively, suggesting that pronounced expression of E-selectin does not occur within 270 min after reperfusion. These results demonstrate sequential expression of three major endothelial cell adherence molecules in situ following myocardial ischemia and reperfusion. The timing of endothelial cell expressed P-selectin and ICAM-1 could coordinate neutrophil trafficking during the early stages of reperfusion. J. Leukoc. Biol. 57: 45–55; 1995.