Abstract: The current study was undertaken to evaluate the clinical, histopathological, hematological and biochemical changes associating BRSV in calves. A total number of 19 calves were subjected to study at private farm (Mosha village, Assiut Governorate, Egypt). Out of them, 13 calves (4 males and 9 females) showed sudden onset of fever and respiratory distress. Sudden death occurred in 4 calves. The remained 6 animals were clinically healthy and represented the control group. Animals were examined clinically and then whole blood and serum samples were collected from all calves under the study. In addition, specimens from lungs, liver and kidneys from dead calves were taken for histopathological and ultrastructural examinations. The present study revealed that bovine respiratory syncitial virus infected both type I and II pneumocyte. The virus induced necrosis in type I pneumocyte and induced proliferation, hypertrophy and necrosis in type II pneumocyte. Infection with BRSV cause hepatic and renal damage and may led to bone marrow depression.