The protocol for this study was designed to evaluate the effects of supportive recall treatments provided with different frequencies, viz. at 3-, 6-, 12- and 18-month intervals. The subjects for the study were recruited from patients attending a public, general dentistry clinic. Prior to baseline, the subjects were given necessary dental treatments to provide a proper baseline for the study. Baseline, intermittent and final recordings included scores of dental plaque, bleeding on probing, probing depth and probing attachment level. Results were evaluated statistically by intergroup comparisons of changes for the various parameters from baseline to final examination after 5 years. The analyses showed some advantage to shorter recall intervals for plaque and bleeding scores. Although not statistically significant, there was a trend suggesting some rebound of sites > or =6 mm deep at the end of the study for the 18-month group, but not for the other groups. Similarly, there was a trend that the 18-month group showed a higher percentage of buccal/lingual furcation sites with attachment loss > or = 1.0 mm than the other groups. Apart from these trends, the analyses failed to demonstrate differences between the groups for either changes of probing depths or probing attachment levels. The negative observations included identification of individuals with 'disease progression' in the various groups, using a series of arbitrary definitions for this parameter. The results of this trial suggest that recall intervals extended to a year may be acceptable for the purpose of reducing periodontal disease progression in individuals with a history of limited susceptibility to the disease.