Serum creatine kinase (CK) and lactic dehydrogenase (LD) isoenzyme concentrations were studied in 44 patients during orthopedic operations that required the application of a pneumatic tourniquet. CK and LD isoenzymes were measured at preoperation, during tourniquet, and after tourniguet release. In the general anesthesia patients, LD isoenzyme values were not significantly changed during and after touniguet release. CK-BB was more significantly increased (p<0.05) after tourniguet (2.65±5. 40IU/l) than at preoperation (0.36±1.17IU/l). In the regional block patients, LD isoenzyme values were not significantly changed during and after tourniguet application. CK-BB was more significantly increased (p<0.05) at after tourniguet (0.90±1.95IU/l) than at preoperation (0.12+0.48IU/l). But regardleas of tourniguet application time, the values of LD isoenzymes were not significantly changed. CK-BB values were more significantly (p< 0.05) increased after tourniguet release than at preoperation, regardless of tourniguet application time.