To investigate whether von Willebrand's Factor (vWF) changes as a result of the reperfusion strategy during acute myocardial infarction (AMI), vWF was measured on days 0, 1, 2, 3, 4, 5 and 15 in 34 patients with AMI. Thrombolysis was initiated in 22 patients and followed by a coronary angiogram 90 min later. In 13 patients the infarct-related artery was then patent (THR group). In nine patients the infarct-related artery was occluded and rescue percutaneous transluminal coronary angioplasty was performed (group THR+rPTCA). In 12 patients, primary PTCA was carried out (pPTCA group). Admission values of vWF were similarly high in the three groups, while changes in vWF over the following days were statistically different among the groups. No significant change was observed in THR, whereas a significant and prolonged increase was found after failed thrombolysis with PTCA (peak increase at day 5:1.54 +/- 0.04 U.ml-1). In the pPTCA group, a significant increase could only be found on day 3 (0.96 +/- 0.04 U.ml-1). Absence of a statistical rise in vWF might be a late indicator of successful thrombolysis. The prolonged increase in vWF after failed thrombolysis needing rescue PTCA probably reflects a higher resistance to thrombolysis, while the slight but significant increase in vWF following primary PTCA could be due to vascular injury.