The feasibility of using the Ramfjord index teeth to estimate whole-mouth periodontal disease activity was investigated. Whole-mouth examinations were carried out semi-annually over a 36-month period in 98 maintenance patients previously treated for adult periodontitis. Recurrent periodontitis was defined as either a 3-mm or greater probing depth increase from baseline, or a 2-mm or greater probing depth increase together with 2-mm or greater of relative attachment loss measured from a reference stent. Whole-mouth disease activity was compared to Ramfjord index teeth data, with and without adjustment. Adjustment was made by multiplying disease activity rates on Ramfjord index teeth by the ratio formed from the sum of all teeth present over the sum of all Ramfjord index teeth in the study population. Without adjustment, Ramfjord index teeth markedly underestimated subjects with recurrent disease activity when compared to whole-mouth findings. However, with adjustment, the hypothesis that upper and lower limits on whole-mouth incidence of recurrent periodontitis could be estimated from Ramfjord index teeth disease-activity rates were not rejected (P > 0.20, z-test) at any 6-month interval. At 5 of 6 examinations, the % of disease active subjects as determined from whole-mouth evaluations was below the upper limit for disease incidence calculated, with 95% confidence, from point estimates derived from adjusted Ramfjord index teeth data. Partial-mouth examinations with appropriate adjustment of Ramfjord index teeth data may be useful for assessing periodontal disease progression in longitudinal population studies of human periodontitis.