Four heroin-overdosed patients presented with coma, elevated serum enzymes (creatine phosphokinase (CPK) and serum glutamic oxaloacetic transaminase (SGOT)), and increased levels of plasma free hemoglobin. In two patients marked myoglobinuria was also detected. The plasma free hemoglobin re-turned to normal levels by the 3rd hospital day. Since coma may eventuate in compression of muscles, we suggest that the disruption of erythrocytes occurs as they traverse these ischemic areas.