The objectives of this study were to determine whether or not dietary clinoptilolite (CPL) has an influence on the levels of calcium (Ca), magnesium (Mg), phosphorus (P), potassium (K) and sodium (Na) in the blood serum of dairy cows during gravidity and early lactation. The study was conducted on 78 dairy cows of Holstein-Friesian breed. The cows were randomly assigned into two groups: the CPL-fed treated group (n = 38) which received 50 g of natural powdered zeolite CPL twice a day from day 180 days before to 60 days after parturition, and the control non-treated group (n = 40). Blood samples were taken on days 180, 90, 60, 30 and 10 before parturition, on the day of calving and on days 5, 12, 19, 26, 33, 40 and 60 following parturition. There were no significant differences in the Ca concentrations between the CPL-fed and the control group. However, after parturition it was noticeable that the Ca concentration was higher in the CPL-fed group, especially on