Recordings of supragingival plaque, bleeding, suppuration and probing depth were obtained for 42 months following initial periodontal therapy. Scores accumulated after various time intervals during monitoring were studied for their predictive value in revealing probing attachment loss as determined by regression analysis during the 0-42 month period. Accumulated plaque scores demonstrated low predictability. Accumulated bleeding scores showed modest predictive values. Suppuration on probing was not a frequent finding during the observation interval and also had modest predictive power. Increase in probing depth compared to baseline and deep residual probing depth had modest predictability after 3 and 12 months, but showed increasing accuracy in revealing probing attachment loss over later time intervals. After a few years of maintenance, increase in probing depth, particularly if combined with high frequency of bleeding on probing, showed the highest predictive value for probing attachment loss of the scores examined.