Synthesis of interstitial collagenase by human fibroblasts was compared when cultured on plastic, in the presence or absence of soluble laminin, on a type I collagen gel and on a gel of basement membrane components (matrigel). Fibroblasts cultured on matrigel or on type I collagen gel displayed an increase in the steady-state levels of mRNA for interstitial procollagenase that was proportional to its enzymatic activity. Laminin, the main component of matrigel, had no effect on the interstitial collagenase synthesis by fibroblasts. We suggest that matrigel, which stimulates the interstitial collagenase production at a transcriptional step, could regulate the catabolic potential of fibroblasts.