A biotyping scheme using improved media and methods for the detection of hippurate hydrolysis, rapid H2S production, and DNA hydrolysis was applied to 1,826 cultures of Campylobacter jejuni, Campylobacter coli and "Campylobacter laridis" isolates from human and nonhuman sources. Four biotypes were identified among C. jejuni: 57.3% of the isolates belonged to biotype I; 36.0%, to biotype II; 4.0%, to biotype III; and 2.7%, to biotype IV. C. coli organisms were differentiated into biotype I (67.0% of the isolates) and biotype II (33.0%). All "C. laridis" isolates belonged to biotype I. The combination of the biotyping scheme with the serotyping of campylobacters provided additional epidemiological markers by further differentiating the serogroups by species and biotypes.