Progesterone is involved in various functions of the cardiovascular system, including those of vascular smooth muscle cells (VSMCs) via progesterone receptor (PR). Progesterone has also been postulated to be involved in inhibition of VSMC proliferation via PR. However, the details of PR expression have remained largely unknown in human cardiovascular VSMCs. Therefore, we first examined the relative levels of PR isoform (PR-A and PR-B) expression in VSMCs, using both immunohistochemistry and quantitative RT-PCR analysis. PR-B was equally expressed between male and female aorta, but PR-A was more abundant in female than in male aorta. This finding demonstrated that the status of PR subtype expression was associated with the difference of genders.