At least seven Campylobacter species have been identified from subgingival sites. Campylobacter rectus has been implicated as a periodontal pathogen; however, association with periodontal infections of other Campylobacter species, especially the newly described Campylobacter showae, is unclear. This study examined which Campylobacter species were associated with periodontal health and disease. Subgingival Campylobacter species from initial and established periodontitis were compared with species from periodontally healthy subjects, including subjects with gingivitis. Campylobacter species were isolated on selective media and identified by whole-cell protein profiles (SDS-PAGE). Except for C. rectus, Campylobacter levels were frequently below the detection limit (2-5% of the microbiota) of non-selective culture methods. C. rectus and C. showae, including Campylobacter X, were found more frequently and in higher levels from diseased than from healthy periodontal sites. C. gracilis was the dominant Campylobacter species found in relatively shallow pockets; however, its presence was unrelated to periodontal health or disease. C. concisus was isolated in higher proportions from relatively shallow and healthy sites, compared with deeper pockets. C. curvus was unrelated to periodontal health or disease. Analysis of the study data confirmed the relationship of C. rectus with diseased subgingival sites and indicated that C. showae may also be associated with periodontal disease.