Losses resulting from pestivirus infections in cattle are of considerable importance to the livestock industry yet, until relatively recently, they have been poorly understood. The escalation of research effort in this field has started to clarify the pathogenesis and epidemiology of the associated diseases but the evolution of understanding is far from complete. Sufficient information exists to indicate the means by which pestivirus infection is introduced to and maintained in populations of cattle. A brief review of current knowledge is given placing particular emphasis on the role played by persistent infections which have resulted from intrauterine infection. The crux of the problem of control is seen to be the avoidance of fetal infection in early gestation. Ways of achieving this which include the immunisation of female cattle with live or inactivated virus vaccines are discussed and areas requiring further work are indicated.