The liver-type phosphofructokinase is a key glycolytic enzyme encoded by genes residing on human and mouse chromosomes 21 and 10 respectively. Genomic DNA regions upstream of the initiator ATG spanning 2.6Kb and 3.4Kb of human and mouse liver-type phosphofructokinase gene were sequenced and analyzed. The proximal 0.4Kb region of both genes featured a CpG island containing 60%-73% GC residues. The first 120 nucleotides preceding the ATG are highly conserved displaying 73% of sequence similarity between human and mouse genes. While this region lacks TATA and CAAT boxes it contains four Sp1 binding sites and was capable of promoting a non regulated expression of the reporter gene chloramphenicol acetyl transferase, in transfection assays. Additional conserved elements were found further upstream at the 5'-region of both the human and mouse genes. They consisted of two Alu repeats and several sequence motifs known to serve as transcription factors binding sites.