The 5' flanking region of the CDC7 gene of Saccharomyces cerevisiae has been sequenced to a point 797 nucleotides upstream of the putative translational initiation codon (designated +1). The sequence reveals a number of symmetry elements between -100 to -380 and two blocks of high local AT content between -29 to -75 and -112 to -144. Transcription initiates heterogeneously at about 10 discrete sites up to 110 nucleotides upstream of the putative translational initiation codon. Some minor transcriptional start sites were also observed between the ATG at +1 and a second in-frame ATG at +55, suggesting that CDC7 may also be translationally heterogeneous. Deletion analysis of the CDC7 upstream region has shown that the gene lacks a functional TATA box, and has identified a 30bp element that is necessary for normal CDC7 promoter function during mitosis. This motif has significant homology with a component of the c-fos promoter which acts to regulate c-fos expression by binding a transcription activating factor. The results suggest that the 30bp motif may play a similar role in regulating CDC7 expression and that there may be similarities between factors that regulate CDC7 expression in yeast and c-fos expression in vertebrate cells.