There are ample genetic and laboratory studies that suggest the PI3K–Akt pathway is vital to the growth and survival of cancer cells. Inhibitors targeting this pathway are entering the clinic at a rapid pace. In this Review, the therapeutic potential of drugs targeting PI3K–Akt signalling for the treatment of cancer is discussed. I focus on the advantages and drawbacks of different treatment strategies for targeting this pathway, the cancers that might respond best to these therapies and the challenges and limitations that confront their clinical development.