The amniotic fluid and placenta are sources of diverse progenitor cell populations, including �mesenchymal, hematopoietic, trophoblastic, and possibly more primitive stem cells. Given that much of the amniotic cavity and placenta share a common origin, namely the inner cell mass of the morula, perhaps it is not surprising that most types of progenitor cells that can be isolated from these two sources also share many characteristics. This chapter focuses solely on the most abundant and easy to isolate progenitor cell population found therein, the mesenchymal stem cells (MSCs). Unlike some of the other stem cell types, MSCs are present throughout gestation. Methods of isolation, expansion, freezing, and thawing of these cells will be presented with preference given to the simplest methods available for any given procedure.