The present study evaluated the clinical stability of healed periodontal pockets over a 3 month time period to determine whether this time interval is appropriate for periodontal maintenance therapy. The clinical characteristics of 128 pockets (3-7 mm depth) distributed in 10 patients, were monitored immediately before and 4, 8 and 16 weeks after a single episode of subgingival root planing. The clinical parameters measured were: pocket depth and bleeding after probing with 15, 25 and 50 gm and manual probing, gingival margin location, clinical attachment level, and gingival and plaque indices. Oral hygiene instruction and supragingival cleaning were given at each time point. An average aggregated score for each subject and for each parameter was calculated at each time point. A repeated measure all within analysis of variance was done, and the Tukey multiple range test was used to assess the significance of differences among and between the means. The significant decreases in plaque, gingival and bleeding indices, and pocket depth as well as the significant gingival recession and gain of clinical attachment which were present at the 4 week point were maintained at 8 and 16 weeks after root planing. It was concluded that the favorable clinical changes which occur in periodontal pockets within 1 month after a single episode of subgingival root planing combined with improved oral hygiene can be maintained for an additional 3 month time period.