A total of 104 fecal specimens from 30 mammals, 12 birds, and 3 reptiles at the Phoenix Zoological Gardens, Miyazaki City, Japan, were examined for the presence of Campylobacter species. All the animals examined were healthy with no fecal abnormality. Twenty-three (22.1%) thermophilic campylobacters, (9 C. jejuni, 11 C. hyointestinalis, 2 C. coli, and 1 C. lari), were isolated from 11 animals (7 mammals and 4 birds). C. jejuni and C. hyointestinalis were the predominant species isolated from these zoo animals and C. hyointestinalis was isolated frequently from simians. As selective media influence the numbers and species of campylobacters isolated, the agar medium was not supplemented with cephalothin. Campylobacters were isolated most frequently when a combination of enrichment culture and selective agar plating was performed at 42 degrees C. For the epidemiological study, a polymerase chain reaction (PCR)-based randomly amplified polymorphic DNA (RAPD) method was used as a tool to detect the heterogeneity of amplified DNAs of Campylobacter spp. isolated from zoo animals. The two arbitrary primers used in this study enabled even closely related strains of the same Campylobacter spp. to be differentiated. RAPD analysis revealed considerable diversity among the strains, suggesting that the transmission of Campylobacter spp. among animals in a defined area occurred through different mechanisms. Examination of the genotypic diversity among the multiple clones from the same host also revealed differences between clones. These results demonstrate that campylobacter populations in zoo animals are highly divergent.