An overview of the concept of cellular immobilization and perfusion as a small laboratory bioreactor model is presented. The cellular systems currently used may be described as static. This is due to conditions of hypoxia and waste product build-up that affect cell physiology. Cellular immobilization and perfusion is, therefore, expected to maintain the cells for very long periods of time under approximately physiological conditions. A number of applications of immobilized perfused hepatocytes and other cellular systems such as adipocytes and Sertoli cells are described in addition to various other cell lines. Moreover, it is suggested that the bioreactor may have potential use as a bioartificial organ.