The efficiency of three commercially available blood culture systems for isolating Campylobacter sp. was investigated. Thirteen of 189,688 blood cultures from patients seen at the Mayo Clinic from 1984 through 1990 were positive for Campylobacter sp. Eleven out of 13 blood cultures positive for Campylobacter sp. were part of a complete three bottle set of cultures (Isolator from Du Pont, Roche Septi-Chek from Hoffman-La Roche, and non-vented Tryptic Soy Broth from Difco), none of them providing a specific microaerophilic mileu. The aerobic Roche Septi-Chek seems to be more efficient for the detection of Campylobacter sp. in blood cultures than either the anaerobic Tryptic Soy Broth (Difco) or the Isolator (Du Pont) using the incubator condition of 5% CO2.