OBJECTIVE The purpose of this retrospective study was to determine the results of 10 years of supportive periodontal treatment(SPT) following active periodontal therapy(APT). Probing pocket depth(PPD), bleeding on probing(BOP), tooth loss(TL)and the effects of two patient-related factors, smoking and gender were evaluated. METHODS This retrospective study examined patients who underwent APT and SPT for adult periodontitis. Analyses were conducted using site-, tooth- and patient-level information. Mean values were calculated, and parametric and nonparametric analyses were conducted as appropriate to assess the results of APT and SPT. RESULTS There was a significant improvement in BOP and PPD after APT. After 10 years, 9.3% of the patients adhered to the SPT protocol. The improvement in BOP and PPD was maintained, with no additional improvement in the clinical parameters at the 10-year follow-up. Furthermore, differences between non-smokers and smokers were found. After the 10-year follow-up, smokers had a significantly higher percentage of sites with a PPD of 4 mm or higher; the mean PPD was also significantly higher in smokers. A significant difference was also found between males and females during SPT for the percentage of sites with BOP and the percentage of sites with a PPD≥6 mm. A minority of patients(18.5%) did not lose teeth, and it was found that molars are the teeth most likely to be lost. The mean number of teeth lost was 2.6 during 10-year follow-up. CONCLUSIONS This study indicates that with regard to bleeding on probing and probing pocket depth, patients receiving supportive periodontal treatment maintain their periodontal condition. However, in this group of adherent maintenance patients, tooth loss was most prevalent for molar teeth.