AbstractGingival crevicular fluid is regarded as a promising medium for the detection of markers of periodontal diseases activity. The collection protocols are straight forward and non‐invasive and can be performed at specific sites of interest in the periodontium. Because the fluid accumulates at the gingival margin, it will contain potential markers derived not only from the host tissues and serum but also the subgingival microbial plaque, and thus an extremely broad range of candidate molecules may be investigated. However, the ability to successfully describe indicators of current disease activity and predictors of future disease is dependent not only upon the choice of the biochemical marker but also on the accurate description of the health status of the sample sites using currently available clinical and radiographic methods. Areas of study which currently show the most promise involve the analysis of host enzyme activities directed against components of the extracellular matrix, the nature of the glycosaminoglycans released into the sulcus and the concentration in gingival crevicular fluid of certain mediators of the inflammatory process, most notably prostaglandin E