The genes coding for plasminogen and apoprotein(a) are clustered, together with two related genes, on the telomeric region of chromosome 6 at band 6q26-27. Moreover, the two genes are 40 Kb apart and transcriptionally pointing to opposite directions. Plasminogen and apoprotein(a) share a high degree of homology in the promoter and 5' flanking regions and their expression is mainly confined to liver. To assess whether common controlling elements mediate the tissue specific expression of these two genes, the region between them was investigated for DNase hypersensitive sites in hepatic cell nuclei.