The quantification of cell proliferation is one essential prerequisite for the research of biomaterial cytocompatibility in vitro. Several methods have been developed for the quantification of cell proliferation and among all of these methods, immunoassay is a rapid, reliable method to assess cell proliferation. Because of the accuracy and the reliability, the quantification of cell proliferation by immunoassay has many distinct advantages and it is widely used in clinical diagnostic and basic research areas. The high resolution data obtained in this assay makes it possible to get a better understanding of cell proliferation.