Although massive genome sequencing efforts have identified the protein kinases encoded by several eukaryotic genomes and proteomic analyses have begun to determine the kinases expressed in a cell, there is still much to learn about the additional cellular events that shape eukaryotic kinomes. Large-scale analyses in Saccharomyces cerevisiae have indicated that a relatively small subset of kinases requires chaperoning by heat shock protein 90 (Hsp90). However, new evidence suggests that most kinases do require chaperoning and, furthermore, that Cdc37, a chaperone that has Hsp90-dependent and -independent functions, serves as the chaperone for a large portion of the yeast kinome.