The plasminogen activating system plays an important role in tissue proteolysis in physiological as well as pathological processes. Earlier studies have shown high concentrations of the plasminogen activator t-PA as well as its inhibitor PAI-2 in gingival crevicular fluid (GCF) In addition, gingival inflammatory reactions have been related to increases in t-PA and PAI-2. In order to explore the potential role of the plasminogen activating system for the development of destructive periodontal disease, the aim of this study was to assess the balance of the activator t-PA to the inhibitor PAI-2 in GCF from patients, clinically defined to represent different periodontal conditions. The Progression Group consisted of 12 periodontitis patients with 1 or more sites having shown an increased pocket depth of ≥ 3 mm during the last 2 years of maintenance care and with ≥ 8 unchanged or improving sites during the period. The Non Progression Group consisted of patients who had shown a decreased or unchanged pocket depth of all sites during the last 3 years of maintenance care. Sampling of GCF was done with small disks of Millipore-filter, and t-PA and PAI-2 were analyzed with ELISAs. There was no difference in the t-PA/PAI-2 ratio between the two groups. However, an intra-individual comparison within the Progression Group showed a higher ratio at the deteriorating sites than at the stable sites Even though no difference was found between the groups, the higher t-PA/PAI-2 ratio at the deteriorating sites in the Progression Group suggests an involvement of the plasminogen activating system in the proteolytic events leading to breakdown of the tooth supporting tissues.