The genus Campylobacter has become increasingly recognised as the cause of various infections. Campylobacter jejuni and C coli cause acute gastroenteritis in man all over the world. C jejuni enteritis can lead to bacteraemia, but its actual incidence remains unknown. Seven cases of bacteraemia caused by C jejuni or C coli are reported, from the blood of seven patients: five immune deficient adults; a newborn baby; and a patient who had had abdominal surgery. Patients who develop diarrhoea as a result of Campylobacter infection are at risk of bacteraemia thereafter.