Collagenolytic activity in human carious and non-carious dentine matrix was compared. Results confirmed the presence of latent collagenase in demineralized dentine and indicated a slow rate of degradation of collagen substrate. Collagenolytic activity was enhanced with the addition of trypsin-TPCK to the demineralized dentine. More activity was observed in the carious dentine, suggesting the presence of collagenase activators or partial enzymic destruction of the inhibitor in the collagen-collagenase-inhibitor complex. It seems that during dentine development collagenase-inhibitor complex is secreted and bound to collagen-dentine matrix, and the enzyme can be activated during the process of dental caries.