Attachment level at two sites on each tooth in 22 untreated subjects with existing periodontal pockets was measured every month for 1 year. Regression analysis was then applied to the data from each periodontal site to determine if statistically significant trends in attachment level change could be detected. 82.8% of the sites monitored did not significantly change during the year. 5.7% of the sites became significantly deeper and 11.5% of the sites became significantly shallower (P less than 0.01) during the period. Among those sites in which pocket depth increased, approximately half exhibited a cyclic deepening followed by spontaneous recovery to their original depth. In 15 of the subjects, sites were found which became significantly deeper while other sites within the same subject became significantly shallower. In six subjects, who might be considered to have an arrested form of periodontal disease, virtually no sites became deeper during the monitoring period whereas 11-36% of their sites became significantly shallower. The results of this investigation suggest that a dynamic condition of disease exacerbation and remission as well as periods of inactivity may be characteristic of periodontal disease.