Kinases and proteases are responsible for two fundamental regulatory mechanisms--phosphorylation and proteolysis--that orchestrate the rhythms of life and death in all organisms. Recent studies have highlighted the elaborate interplay between both post-translational regulatory systems. Many intracellular or pericellular proteases are regulated by phosphorylation, whereas multiple kinases are activated or inactivated by proteolytic cleavage. The functional consequences of this regulatory crosstalk are especially relevant in the different stages of cancer progression. What are the clinical implications derived from the fertile dialogue between kinases and proteases in cancer?