Abstract Matrix metalloproteinases (MMPs) and serine proteinases seem to be related to tissue destruction in periodontitis. The presence of MMPs in gingival crevicular fluid (GCF) and saliva, however, has not been studied comprehensively with the enzyme-linked immunosorbent assay (ELISA)-technique, We therefore examined the levels of MMP-1,-3.-8 and -9, and their endogenous inhibitor, tissue inhibitor of matrix metalloproteinases (TIMP-1). in GCF and saliva of patients with adult periodontitiss (AP) and localized juvenile periodontitis (LJP). Elevated levels of MMP-1 were detected in LJP GCF compared to AP and control GCF. Elevated levels of TIMP-1 were also detected in LJP GCF in comparison to AP and control GCF Higher MMP-8 levels were detected in AP GCF compared to LJP and control GCF. The relative low levels of MMP-3 were present in all studied GCF samples. Elevated levels of MMP-8 were further detected in saliva of AP compared to LJP and the controls. Both MMP-1 and TIMP-1 were detected in all studied saliva samples, but not significant differences were detected between the studied groups. Our ELISA-results confirm that (i) PMN MMP-8 and MMP-9 are the main collagenase and gelatinase in AP GCF, whereas GCF collagenase in LJP seems to be of the MMP-1-type; (ii) only low levels of TIMP-1. endogenous MMP-inhibitor. are present in AP GCF. which emphasises the importance of doxycycline as a possible adjunctive drug in the treatment of AP patients; (iii) tests based on specific antibodies against PMN MMPs. especially MMP-8, might serve as a reliable method of measuring and monitoring enzyme levels in GCF from different periodontitis patients.