1. The release of bradykinin (BK) and its metabolite, des-Arg9-bradykinin (des-Arg9-BK), was studied following reperfusion of a globally ischaemic rat heart. 2. BK-like immunoreactivity increased from 13 +/- 3 (preischaemic value) to 48 +/- 12 fmol min-1 g-1 (P < 0.05, n = 14) 30 s after reperfusion. No difference in BK release was found between control hearts and hearts pretreated with the angiotensin converting enzyme (ACE or kininase II) inhibitor, enalaprilat (50 ng ml-1). 3. No significant change in des-Arg9-BK-like immunoreactivity during reperfusion was observed in control hearts. In contrast, des-Arg9-BK-like immunoreactivity rose from 44 +/- 15 to 177 +/- 61 fmol min-1 g-1 (P < 0.05, n = 7) 30 s after reperfusion in enalaprilat-treated hearts. 4. In conclusion, BK is released upon reperfusion of the globally ischaemic rat heart. ACE inhibitors, through the inhibition of kininase II, increase the formation of the active metabolite, des-Arg9-BK.