This study was carried out to investigate the effect of dry oak leaves on some clinical, haemotological and biochemical parameters in cattle. In the study. 3-6 years aged crossbred cows breeding in the family administrations of Gözeli and Çortunlu villages in Elazığ province, allocating 30 cows in the group offered dry oak leaves (Quercus infectoria and Quercus brantii) (experimental group) and 10 cows in the group offered no dry oak leaves (control group) were used. Dry oak leaves were offered 2 kg daily for each cow mixing with straw. Systematic clinical examinations and laboratory analysis were made for all Ihe cattle. Ruminal fluid examinations (pH. total number of infusoria, CI' concentration), haematological examinations (haematocrit values, amount of haemoglobin, total leucocyte counts and total erythrocytes counts) and biochemical examinations (serum K\ Na', Ct% Ca+*, inorganic P, Zn, Fe, creatinine, BUN and total protein) were perfoimed. All the parameters were found to be generally within the normal range as reported for cattle. However, in clinical and haemotological examinations, a significant decrease (p<0.05) was found in ruminal motility, total infusoria number, hematocrit values, amount of hemoglobin and total erythrocytes counts in expenmental group. In biochemical analysis, a significant increase (p<0.05) in K+, inorganic P, total protein, creatinine and BUN values, a significant decrease (p<0.05) in Ca+-value, an insignificant decrease (p>0.05) in Fe and Zn values were found in experimental group. In conclusion, clinical, haematological and biochemical parameters were determined to be in physiological limits in cattle by offering dry oak leaves at these amounts.