The proto-oncogene c-fos is an immediate-early gene that becomes activated by a wide variety of extracellular stimuli. Since many studies regarding regulation of c-fos are conducted in vivo using rats, or with rat cell lines, we have cloned the rat c-fos gene in order to verify that the same regulatory elements that have been characterized in the human and mouse c-fos promoter are also present and functional in the rat. The nucleotide (nt) sequence of the 5'-flanking region of the rat c-fos gene displays remarkable similarity with the mouse and human c-fos genes (93 and 77% identity, respectively). cis-Acting regulatory elements, such as the sis-inducible element element (SIE), serum-response element (SRE), AP-1-recognition site, calcium/cAMP-response element (Ca/CRE) and TATA box are present in the rat c-fos 5'-flanking region. A putative glucocorticoid-response element (GRE) is present 13 bp downstream from the AP-1-recognition site.