Biomarkers of periodontal disease activity may be obtained from potential proteolytic and hydrolytic enzymes of inflammatory cell origin. Studies that have sought to correlate these enzymes with periodontal disease activity are reviewed with special consideration given to collagenases, cysteine, aspartate and serine proteinases, beta-glucuronidase, arylsulphate, alkaline and acid phosphatases, myeloperoxidase, lysozyme and lactoferrin.