Objective To investigate the protective effects of warm oxygenated leukocyte-depleted blood cardioplegia on myocardium during cardiac valve replacement. Methods Forty patients of both sexes undergoing elective valve replacement under CPB were randomly allocated into two groups (n = 20 each) : control group and study group. Warm blood cardioplegia was used in both groups, while in study group the leukocytes in the blood used for cardioplegia were depleted with FT-RL type leukocyte filter. The T0 of the cardioplegic solution was maintained at 32-35℃. Blood samples were taken for determination of plasma concentrations of human heart fatty acid-binding protein (HH-FABP) and malonaldehyde (MDA) and myocardial tissue was obtained from right atrium for determination of myeloperoxidase (MPO) activity before aortic cross-clamping (T0), immediately after (T1) and 30 and 60 min after aortic unclamping (T2 ,T3).Results The two groups were comparable with regard to sex, age, body weight, height, cardiac function and CPB and aortic cross-clamping time. The plasma concentrations of HH-FABP and MDA were significantly increased after aortic unclamping (T2,3) compared to the baseline (T0) in both groups but were significantly lower in study group than in control group (P