The role played by contaminated hypodermic needles and nose tongs in the spread of bovine viral diarrhoea virus was investigated by using a persistently viraemic animal as a virus donor. Susceptible cattle were infected by using contaminated needles and tongs and in some instances they in turn infected animals kept with them. Non-biting flies which fed on the ocular secretions of a persistently viraemic animal were also shown to be contaminated with the virus.