Various methods for the prevention of milk fever (MF) in dry dairy cows are available. We decided on intramuscular (i/m) administration of high vitamin D3 doses and oral administration of anionic salts. On three dairy farms with similar dietary treatments these two methods were applied in 30 Black and White cows. The first experimental group of cows (n = 10; DCAD =+95.99 mEq/kg DM) was given 10 ml Duphafral® Vit. D3 1000 (i/m) one week before the expected calving. The second group (n = 10; DCDA = –99.00 mEq/kg DMI) was orally administered 300 g of anionic salts (KatAn® ) per day two weeks before calving. The third group of cows (n = 10, DCDA =+95.99 mEq/kg DMI) was the control group. During the experimental period we controlled the clinical status of cows and venal blood samples were taken (2 and 1 week before parturition, 1, 2 and 7 days postpartum) for the determination of Ca, iP and Mg values. It was established that best preventive results were achieved by i/m application of vitamin D3. Only one cow from this group was two days after parturition affected by MF; in serum we found 1.47 mmol/L Ca; 0.71 mmol/L iP; 1.37 mmol/L Mg. In KatAn® group one cow was affected by typical MF (1.65 mmol/L Ca; 1.40 mmol/L iP; 1.25mmol/L Mg) the first day after calving and one cow showed retained foetal membranes. In the control group the incidence of the diseases was considerably higher. One cow had MF (1.34 mmol/L Ca; 0.83 mmol/L iP; 1.48 mmol/L Mg), one had retained foetal Membranes and one cow showed left-side displacement of the abomasums within one week after calving. On the basis of the analyses of clinical-laboratory data we are of the opinion that the best prophylactic measure for the prevention of milk fever and with it related diseases on small and medium large farms in Slovenia is i/m administration of high doses of vitamin D3.