A biotyping scheme has been developed which utilises 12 tests, including growth at 28°C, hippurate hydrolysis, and 10 resistotyping test. These tests are arranged in groups of three, and by assigning a numerical value to each positive tests a four figure code is produced for each strain. The order of the tests is such that campylobacters are both speciated and biotyped. This scheme recognises Campylobacter jejuni, C coli, 'C laridis', C fetus fetus, and C fetus subspecies venerealis. The reproducibility of the biotyping technique and the stability of the biotype code have been determined by testing campylobacter reference strains. The routine application of the scheme has also been evaluated by biotyping 1000 recent campylobacter isolates, and the epidemiological value has been confirmed by testing serotyped isolates from several milk borne outbreaks.