The p27 Kip1 Colorimetric Cell-Based ELISA Kit provides a lysate-free, convenient, and high-throughput approach for sensitive detection of p27Kip1 protein expression profile in cells. The kit can be used for measuring the relative amounts of p27Kip1 in cultured cells as well as screening for the effects that various treatments, inhibitors (ie siRNA or chemicals), or activators have on p27Kip1.