An outbreak of Crimean-Congo haemorrhagic fever (CCHF) on a dairy farm in the Orange Free State in 1984 is described. Forty-six cows were purchased from the western Cape Province in January 1984; 2 died from the tick-borne disease anaplasmosis in March and a labourer who helped butcher the carcasses became ill a few days later. Another cow died at the end of April and within 9 days 4 people who had come into contact with its blood became ill. Antibodies to CCHF virus were found in the sera of the 5 patients but not in other residents of the farm. Three patients recovered from a severe influenza-like illness without seeking medical attention; 1 patient, who was admitted to hospital, recovered from illness marked by haematemesis, epistaxis and amnesia and the 5th patient died of complications of surgery for brain haemorrhage. Antibody studies indicated that many of the cows became infected with CCHF after their arrival on the farm. It can be deduced that animals reared in tick-free, or relatively tick-free, circumstances, which are then moved to where they are subject to heavy parasitization by ticks, can acquire common tick-borne diseases of livestock plus CCHF infection simultaneously. In such circumstances there is a definite risk of human exposure to CCHF-infected blood or other tissues.