Infectious calf pneumonia is a high-mortality pneumonia of housed dairy-type calves. Viruses are important etiologic agents and infection with bovine respiratory syncytial virus (RSV) and parainfluenza type 3 virus (PI-3 virus) may result in extensive, and sometimes fatal, lung damage. Respiratory viral infections are frequently followed by mycoplasmal and secondary bacterial invasion of the lower respiratory tract, which increases the extent and severity of lung damage. Bad housing, particularly bad ventilation, will increase the severity of pneumonia outbreaks. Although the source of respiratory viral infections is not always obvious, it is likely that a proportion of calves acquired infection from their dams early in life. The possibility of cross-infections from other domestic animals and from humans must also be considered. Diagnosis of respiratory virus infections necessitates submission of suitable respiratory tract specimens that are taken at an early stage in the outbreak together with paired sera. Various therapeutic and prophylactic regimens for the control of calf pneumonia are described.