The protein encoded by the c-ets1 proto-oncogene is a member of a new family of transcription factors. Cellular regulatory sequences responsive to the c-Ets1 proteins include a urokinase-type plasminogen activator (uPA) gene enhancer, the stromelysin 1 and the collagenase 1 gene promoters. During normal as well as pathological development, the expression of c-ets1 is associated with the occurrence of invasive processes, either in invading cells or in the invaded tissue. Since these invasive processes are thought to require the remodeling of the extracellular matrix, we investigate the relationships between c-Ets1 and the expression patterns of transcripts encoding the matrix-degrading proteases uPA, stromelysin 1 and collagenase 1, in embryos and in solid tumors.