Among the dendritic cell (DC) subsets, plasmacytoid DCs are thought to be important in both generating antiviral and antitumor responses. These cells may be useful in developing dendritic cell-based tumor vaccines, however, the rarity of these cells in the peripheral blood have hampered attempts to understand their biology. To provide better insight into the biology of plasmacytoid DCs, we isolated these cells from the peripheral blood of healthy donors in order to further characterize their gene expression. Using gene array technology we compared the genetic profiles of these cells to those of CD14+ monocytes isolated from the same donors and found several immune related genes upregulated in this cell population. Understanding the genetic profiles of this dendritic cell subtype as well as others such as the BDCA-1 expressing myeloid DCs may enable us to manipulate these cells ex-vivo to generate enhanced DC-based tumor vaccines inducing more robust antitumor responses.