Epithelial cells are present in many different tissues in the body, and possess a diverse number of functional properties. However, all epithelial cells share some common characteristics. The cells possess a morphological polarity (an-apical and basolateral surface), and are interconnected by tight junctions. The epithelial cells also possess the capacity to transport select solutes across the monolayer. Transport systems localized on either the apical or basolateral surface are respon­ sible for this vectorial transport. Such characteristics of epithelial cells can be examined in the tissue culture situation. This volume discusses the use of cell culture techniques to study these fundamental properties of epithelial cells. Ma­ jor questions concerning epithelia which may be examined in culture are ad­ dressed. The approaches which are taken to answer these questions are described in detail with regards to kidney cell cultures. Similar investigations may be done with epithelial cell cultures derived from other tissues, following the kidney cell culture paradigm.