We examined the promoter activity of two homologous plasminogen-related genes (PRGA and PRGB) employing HepG2 cells. The 5'-flanking regions of these genes were sequenced first, then inserted into the upstream region of the CAT gene in an expression vector. CAT assays revealed that the promoter activity of PRGA was 3-fold that of plasminogen, while the activity of PRGB was 5-fold. Deletion analysis of these genes demonstrated that a region between -283 and +153 bp relative to the transcription initiation site was essential for their expression, and that there were regions with either negative or positive effects on expression farther upstream.