One hundred and three calves and heifers persistently infected with BVD virus were examined. The most important clinical findings in order of frequency were weight loss, erosions of the oral mucosa, diarrhea, anorexia and fever. In addition, nasal discharge, lymph node enlargement, erosions of the nose, muzzle and interdigital cleft and bronchopneumonia occurred in less than half of the patients. Furthermore, crustaceous dermatitis was observed in three patients and petechial hemorrhage of the oral mucosa occurred in two other cases with severe thrombocytopenia. Haemoconcentration, leukocytosis, hyperfibrinogenemia and azotemia were the most important haematological findings. To confirm the clinical diagnosis, the serum antibody titre of 69 patients was compared with that of a clinically healthy control animal from the same herd. There was no positive antibody titre in 65 of the 69 patients, whereas 67 of the control animals had positive titres. In 34 patients, EDTA blood samples were collected for virus detection. In 20 of these, skin biopsy samples were also obtained for virus demonstration. Virus has been demonstrated in the blood of 32 of the 34 cases and in all 20 skin biopsy specimens.