BACKGROUND Calendula officinalis is commonly called the marigold. It is a staple topical remedy in homeopathic medicine. It is rich in quercetin, carotenoids, lutein, lycopene, rutin, ubiquinone, xanthophylls, and other anti-oxidants. It has anti-inflammatory properties. Quercetin, one of the active components in Calendula, has been shown to inhibit recombinant human matrix metalloproteinase (MMP) activity and decrease the expression of tumor necrosis factor-α, interleukin-1β (IL), IL-6 and IL-8 in phorbol 12-myristate 13-acetate and calcium ionophore-stimulated human mast cells. OBJECTIVE To examine the effects of Calendula on human gingival fibroblast (HGF) mediated collagen degradation and MMP activity. METHODS Lactate dehydrogenate assays were performed to determine the non-toxic concentrations of Calendula, doxycycline and quercetin. Cell-mediated collagen degradation assays were performed to examine the inhibitory effect on cell-mediated collagen degradation. Gelatin zymography was performed to examine their effects on MMP-2 activity. The experiments were repeated three times and ANOVA used for statistical analyses. RESULTS Calendula at 2-3% completely inhibited the MMP-2 activity in the zymograms. Doxycycline inhibited HGF-mediated collagen degradation at 0.005, 0.01, 0.02 and 0.05%, and MMP-2 activity completely at 0.05%. Quercetin inhibited HGF-mediated collagen degradation at 0.005, 0.01 and 0.02%, and MMP-2 activity in a dose-dependent manner. Calendula inhibited HGF-mediated collagen degradation and MMP-2 activity more than the same correlated concentration of pure quercetin. CONCLUSIONS Calendula inhibits HGF-mediated collagen degradation and MMP-2 activity more than the corresponding concentration of quercetin. This may be attributed to additional components in Calendula other than quercetin.