A DNA fragment containing a promoter region for human polypeptide chain elongation factor-1.alpha., its base sequence and expression plasmids containing the DNA fragment having high applicability to a wide range of host cells with high expression capacity. These expression plasmids can be maintained stably for at least one month in mammalian host cells. Such features of the expression plasmids may render possible the efficient production of various kinds of useful physiologically active substances for a long period using wide range of mammalian cells as the host.