We undertook a retrospective study of 36 victims of high-voltage electrical contact injuries to determine the incidence and possible source of elevated creatine kinase (CK)-MB enzyme in their serum. Only two sustained myocardial infarctions (one late) according to history, electrocardiographic findings, and clinical course. Serum lactate dehydrogenase isoenzyme levels were abnormal but revealed no myocardial infarction patterns. Creatine kinase total activity, however, reached 1.5 to 1,140 times normal in 92% and the CK-MB level was abnormal in 50% despite the low incidence of myocardial damage. Skeletal muscle CK and CK-MB levels in four nonelectrically injured patients were comparable to those in normal muscle while CK and CK-MB activity was elevated in six such electrical injuries. There was a gradient in CK-MB activity with greatest CK-MB activity in "normal" muscle near the injury site, lesser amounts in border tissue, and least in the worst-injured site. We conclude that myocardial injury is uncommon in high-voltage electrical injury and skeletal muscle injured by high electrical voltage is stimulated to produce, as well as release, CK-MB.