Many growth factor-inducible immediate-early genes, including c-fos, encode transcription factors that are believed to propagate the mitogenic signal by activating a program of gene expression critical for cell proliferation. This review summarizes work aimed at elucidating the molecular mechanisms by which a growth factor-induced signal effects a change in gene expression. In the case of c-fos, both the activation and repression of transcription are mediated by the serum response element, a dyad symmetrical sequence found upstream of the c-fos gene. This element binds a complex of proteins, a component(s) of which may be the target of the growth factor-induced signal. Recent progress made towards understanding the roles of these factors in the regulation of c-fos transcription will be described.