We have examined the effect of interleukin-6 (IL-6) on the synthesis of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMP) by human skin fibroblasts, both at protein and messenger RNA levels. IL-6 did not modulate the production of MMPs and TIMP. Furthermore IL-6 did not modify the stimulatory effect exerted by interleukin-1 (IL-1) on the expression of MMPs and TIMP. These results strongly suggest that IL-6 is not involved in the extracellular matrix breakdown, either directly by acting on cell production of MMPs or TIMP, or indirectly by modulating the effect of IL-1 on the synthesis of MMPs and TIMP.