The p53(Phospho-Ser366) Colorimetric Cell-Based ELISA Kit provides a lysate-free, convenient, and high-throughput approach for sensitive detection of p53(Phospho-Ser366) protein expression profile in cells. The kit can be used for measuring the relative amounts of p53(Phospho-Ser366) in cultured cells as well as screening for the effects that various treatments, inhibitors (ie siRNA or chemicals), or activators have on p53(Phospho-Ser366).