During the course of studies to reproduce proliferative enteritis in hamsters, Campylobacter cinaedi was recovered from the feces of the majority of healthy hamsters obtained from two commercial sources. The organisms were cultured by using filtration, a nonselective medium, and a microaerophilic atmosphere containing hydrogen. Isolation was hindered by the fastidious nature of C. cinaedi and by the presence of other Campylobacter species in the hamster intestine. All hamster C. cinaedi isolates were phenotypically similar to C. cinaedi ATCC 35683. Comparison of whole-cell protein profiles of one hamster isolate with a reference strain of C. cinaedi by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting with C. cinaedi-specific rabbit antiserum supported the phenotypic identification of these isolates. Hamsters may be an animal reservoir for human C. cinaedi infections.