Objective: To observe the metabolism of carnitine in patients with chronic renal failure(CRF).Methods:The plasma free carnitine(FC) concentrations were monitored in the undialyzed and dialyzed patients with CRF and normal subjects.Results: (1)Plasma FC concentration in undialyzed patients with CRF was significantly higher than that in normal subjects(P<0.05),and it was closely correlated with blood urea nitrogen(r=0.666 0) and uric acid(r=0.642 0,P<0.05),not correlated with serum creatinine.(2)Predialysis plasma FC concentration in dialyzed patients was much lower than that in normal subjects and undialyzed patients(P<0.01),postdialysis plasma FC concentration was significantly lower than predialysis concentration(P<0.001). There was a 70%decline in plasma FC concentration during one hemodialysis session.Furthermore,plasma FC concentration was very significantly correlated with dialysis time(r=-0.879 3,P<0.001),not correlated with creatinine clearance rate. Conclusion: There is obvious carnitine metabolism disturbance in patients with CRF,especially in hemodialyzed patients whose plasma FC was deficient.So,it is essential for hemodialyzed patients to be timely supplemented with carnitine after hemodialysis.