In a cross sectional study in 38 cow-calf farms blood and fecal samples were taken from 207 calves at an age of 8-10 months and their darms, in order to determine the seroprevalence of Leptospira hardjo, Coxiella burnetii, Toxoplasma gondii and the presence of the BVD-Antigen as well as the prevalence of endoparasites. The study was conducted in fall 1994 at the end of the grazing period. Eggs or larvaes of gastrointestinal helminths were detected in 74% of calves that were dewormed before the grazing period and in 88% of untreated calves. The difference between the two groups was statistically significant. In 83% of the weaned calves oocysts of Eimeria spp. were diagnosed. No significant difference in weight gain was observed between animals without endoparasites and animals infected with either helminths and/or Eimeria. In cows the prevalence was 61.5% for helminths and 45.7% for Eimeria spp. In calves the seroprevalence was 4% for Leptospira hardjo, 0.5% for Coxiella burnetii and 14.0% for Toxoplasma gondii. The seroprevalence in cows were 18% for Leptospira hardjo, 7.6% for Coxiella burnetii and 14.3% for Toxoplasma gondii. The prevalence of the BVD-Virus antigen was 0.5% for calves and cows.