The aim ol this study was to determine the relationship between the levels of vilamin C of plasma, mononuclear leukocytes (MNL) and polymorphnuciear leukocytes (PMNL) with some biochemical parameters in cows,In this study, 22 Holstein heifers at the age of 2-3 years were used at the same feeding regimer, the blood samples were drowned from V. jugularis. The vitamin C levels of MNL, PMNL and plasma were analysed by spectrophotometry method, the plasma glucose, cholesterol, total protein and albumin concentrations were analysed by autoanalyser. The vitamin C levels of plasma, MNL and PMNL were 4.97 ± 0.29 pg/ml, 0.479 ± 0.055 pg/cell, 0.040 ± 0.004 pg/cell, respectively, plasma glucose, cholesterol, total protein and albumin concentrations were 93.59 ± 1.56 mg/dl, 114.50 ± 6,04 mg/dl, 6.84 ± 0.12 g/dl, 3.48 ± 0.03 g/dl, respectively.The positive correlation between MNL and plasma vitamin C levels (p<0.01) and negative correlation between MNL and PMNL vitamin C levels (p<0.01) has been observed. In addition, there were negative correlation between plasma total protein concentration and the vitamin C levels of plasma (p<0.0t) and MNL (p<0.01) and positive correlation between plasma total protein and plasma glucose levels (p<0.05). In conclusion, it is useful the determine the vitamin C levels of MNL and PMNL together with plasma vilamin C levels lor investigating the vitamin C levels in the body.