The effects of 15 minute periods of coronary artery occlusion on plasma creatine kinase (CK) and CK-MB isoenzyme activity, regional myocardial function and subsequent myocardial necrosis were studied in six conscious baboons 2 to 3 weeks after recovery from instrumentation. Mid left anterior descending coronary artery occlusion induced complete loss of systolic wall thickening (ultrasound transit time technique) and decreases in epicardial (-93%) and endocardial (-96%) blood flows (microsphere technique). Reperfusion after 15 minutes resulted in complete recovery of regional function 24 hours later. Serial plasma enzyme activity revealed a significant increase in total CK from 71 +/- 11 to 976 +/- 158 U/liter and in CK-MB from levels that were too low to measure to 21.4 +/- 2.9 U/liter. At autopsy, neither gross pathologic evidence (triphenyltetrazolium chloride staining technique) nor histologic evidence of myocardial necrosis was observed. Thus, in the conscious baboon short episodes of myocardial ischemia are associated with a significant appearance of CK and CK-MB in the blood in the absence of cellular necrosis.