Extracellular matrix component is degraded by enzymes of thematrix metalloproteinases(MMPs). MMPs are produced by both hemopoietic and structural cells. Increased activity of MMP-3 in periodontium is strongly associated with inflammatory periodontal disease. The purpose of the present study was to determine the effect of tetracycline analogues on the activity of MMP-3. Tetracycline-HCl, doxycycline-HCl, and minocycline-HCl were applied to huamn gingival fibroblasts at various concentrations of 10, 25, 50, 100, 200${mu}g$/ml, and 1 hour later IL-$1{eta}$ of 25ng/ml was added. After incubation for 24 hours the cells were reacted by enzyme-linked immunosorbent assay using proMMP-3 ELISA kit. The optical density was measured by microwell plate reader at 450nm. The relative activity of MMP-3 was calculated as the percentage of the optical density of each experimental group to that of the control. The difference of the optical density and the relative activity of MMP-3 between the experimental groups and the control wasstatistically analyzed by one way ANOVA. The results were as follows: 1. Tetracycline-HCl showed the tendency to inhibit the activity of MMP-3 at the concentration lower than 25${mu}g$/ml, but increased significantly the activity of MMP-3 at the concentration of 200${mu}g$/ml(p<0.05). 2. Doxycycline-HCl inhibited significantly the activity of MMP-3 at the concentration lower than 100${mu}g$/ml, but increased significantly the activity of MMP-3 at the concentration of 200${mu}g$/ml(p<0.05). 3. Minocycline-HCl inhibited the activity of MMP-3 at the concentration in the range of 10 to 200${mu}g$/ml. Within the limit of the present study, the above results suggested that the low concentration of tetracycline analogues could inhibit the activity of MMP-3 induced by IL-$1{eta}$ in human gingival fibroblasts.