Campylobacter species such as C. jejuni and C. coli are recognized as major causes of acute gastroenteritis world-wide. Although C. jejuni and C. coli are usually non-pathogenic in birds and animals, they cause enteric disease in humans and the source of infection is often the consumption of contaminated foodstuffs. In this paper we report on the development and use of a multiplex PCR of C. jejuni genomic DNA which yielded a PCR product with a unique polymorphic site that can be used to quickly and accurately identify and group C. Jejuni isolates from any source including DNA, cell culture, skin washings and faecal samples. The test is simple and sensitive and can detect purified DNA from a single bacterium 10(2) cells from crude lysates, 10(3) cells in seeded faeces and 120 cells/ml of washing of 1 cm2 skin fragments of chicken skin.