A cell culture inside a three-dimensional gel of fibrillar collagen is an experimental model used to study the response of cells to the extracellular matrix. Many cell types induce the contraction of gel and simultaneously decrease their production of type I collagen, whereas the expression of interstitial collagenase (matrix metalloproteinase-1; MMP-1) is enhanced. We have previously shown that in osteogenic cells the collagen receptor alpha2beta1 integrin is a positive regulator of MMP-1 and that the number of alpha2beta1 integrins on the cell surface also regulates the magnitude of contraction. However, the downregulation of collagen mRNA levels is not initiated by alpha2beta1 integrin. Here, we have studied in human KHOS-240 and MG-63 osteosarcoma cells and in human skin fibroblasts the effects of tyrosine kinase inhibitors on collagen gel contraction and on the regulation of MMP-1 and collagen alpha1(I) genes by extracellular collagen. The induction of MMP-1 could be inhibited by all tyrosine kinase inhibitors tested with the exception of genistein. None of them could prevent the downregulation of collagen expression. Thus, the collagen-induced alterations in the expression of MMP-1 and collagen alpha1(I) seem to be dependent on distinct signal transduction pathways. Many of the inhibitors, including genistein, could prevent the contraction of collagen gels. The effect was not related to their ability to inhibit cell growth, because an inhibitor specific for DNA synthesis and cell division did not have the same effect. Thus, we suggest that the process of collagen gel contraction requires protein-tyrosine phosphorylation and that the ability of cells to contract collagen gels is not related to the induction of MMP-1 or to the level of collagen alpha1(I) expression. Finally, we propose that the tyrosine kinase inhibitors might be considered as candidate molecules in the treatment of pathological scar contraction.