In a previous study, an edentulous subject showed the presence of P. gingivalis, only in saliva. The present case report is a longitudinal follow-up on this proband (female, 63 years) and her spouse with periodontitis (67 years). Samples were taken from the proband and the spouse for microbiological analysis at several occasions during a 3-year period and a 1-year period respectively. In the edentulous proband, P. gingivalis was present in saliva only, at all times. In the spouse, P. gingivalis was present in the periodontal pocket and on the mucous membranes, but the saliva was culture-negative for this species at both sampling times. The restriction enzyme analysis (REA) patterns of isolates (n=7) of P. gingivalis from the proband recovered over 3 years showed no differences. This indicated that the same clonal type of P. gingivalis persisted for 3 years in the proband. The P. gingivalis isolates (n=13) from the spouse showed no differences when REA patterns were compared. Comparison of REA patterns from the proband and the spouse also showed no differences. Thus the same clonal type of P. gingivalis can persist over several years in an edentulous subject and at least for 1 year in a subject with periodontal disease.