During the last few years, a variety of technologies have been developed for rapid discovery of protein kinase inhibitors from both synthetic small-molecule libraries and natural products (1 –8 ). Many of high throughput kinase assays have been developed in 96-, 384-, and 1536-well formats using these technologies (9 –11 ). Development of these technologies allow one to quickly large synthetic compound or natural product libraries in a very short period of time with high sensitivity, accuracy, and reproducibility. Therefore, development of these new technologies has significantly accelerated the process of discovering drug leads for kinases. In this chapter, I will summarize and compare a number of technologies for development of homogeneous, high-throughput kinase assays.