While it has been postulated that lyso-PAF and PAF might contribute to structural and functional damage in myocardial ischaemia, there has been no clear evidence for the accumulation of these bioactive compounds in ischaemic myocardium. In open chest, anaesthetised dogs, the proximal left anterior descending coronary artery was ligated and myocardial samples from the central ischaemic and normal areas assayed for lyso-PAF, free arachidonic acid and PLA2 activity. Ischaemic myocardium contained 50 +/- 29% (SD) more lyso-PAF than non-ischaemic myocardium after 20 min ischemia (P less than 0.002; N = 8) and 53 +/- 39% more after 60 min (P less than 0.01; N = 8) but there was no difference after 10 min (N = 8). Free arachidonic acid significantly increased in ischaemic myocardium after 60 min (122 +/- 136%; P less than 0.05) while no increase in PLA2 activity was found in-vitro. Since lyso-phospholipids themselves damage cell membranes and, additionally, lyso-PAF is the precursor of PAF which has potent effects on platelets, leukocytes and small vessels, the increase in lyso-PAF in ischaemic myocardium could contribute to myocardial damage.