Extract of Tan-Shen (Salvia miltiorrhiza, Labiatae), a Chinese traditional crude drug, was reported to show beneficial activity for heart disease. Chemical examination on the extract was performed on the basis of screening for protective action on the ischemic myocardium. Isolated hearts were subjected to hypoxic perfusion for 20 min, followed by 45 min reoxygenation, and the recovery of cardiac contractile force and changes in UV absorbance of the perfusate were examined. Among the components isolated, tanshinone I, cryptotanshinone, and tanshinone VI elicited a significant enhanced recovery of the contractile force upon reoxygenation. This was associated with a decrease in the increase in UV absorbance of the perfusate, suggesting the preservation of ATP metabolites in the myocardium. This, in turn, may enhance the restoration of ATP upon oxygen-replenishment. The results suggest that tanshinone I, cryptotanshinone, and tanshinone VI can protect the myocardium against ischemia-induced derangements.