Abstract： Objective　To study the changes of arterial blood lactate(ABL) and serum enzymes activities and thier correlation.Method　Lactate dehydrogenase(LDH),alkaline phosphatase(AKP) and creatine kinase(CK) in serum were determined in sixty-four critical patients in the intensive care unit(ICU) at admission immediately,following 24h,48h and 72h,respectively.The patients was divided into three groups:favorable,survival and death groups.Results　Before treatment,ABL level was(3.9±2.5,2.9±1.3 and 3.8±2.3)mmol/L in favorable,survival and death groups respectively.Although ABL in favorable and survival groups were decreased gradually to normal level during 24～72h,the death group showed that the decline was very slowly it still persistent elevated in 72h.There was significanct difference between the death group and the favorable and survival groups(P＜0.05 or P＜0.01).AKP had significant difference between favorable and death groups(P＜0.05 or P＜0.01) in 24～72h.LDH and CK increased in three groups and there was significantly difference between the death group and the favorable and/or survival group(P＜0.05 or P＜0.01).The relationship of ABL to AKP in 48～72h,ABL to LDH in 24～48h was positive correlation,and ABL to CK in 24～72h was negative correlation.Conclusions　We conclude that the significance of ABL for prognosis in critical illness dependent on the rapid of ABL' elimination.The ABL is slowly eliminated,or increased continually,and the LDH,AKP,CK the more are release,the more worse the patients' condition and prognosis.So it is that more multiple organ disorder syndrome(MODS) or multiple organ failure(MOF) occurred easily in the death group.The high ABL level with the high tissue release enzymes has better clinic value to judge the degree and prognosis of critical illness.