Oval cells and small hepatocytes (SHs) are well known as hepatic stem/progenitor cells. However, the relationship between the oval cells and SHs in liver regeneration is not well understood. To resolve this issue, we established a technique to selectively separate oval cells and SHs. In the injured rat liver, oval cells and SHs transiently appear in the initial period of liver regeneration. Thy1(+) and CD44(+) cells are candidates for markers of oval cells and SHs, respectively. In this chapter, the methods for sorting and culture of the cells are described in detail.