The treatment of patients with advanced non–small cell lung cancer (NSCLC) harboring chromosomal rearrangements of anaplastic lymphoma kinase (ALK) has been revolutionized by the development of crizotinib, a small molecule inhibitor of the tyrosine kinases ALK, ROS1, and MET. Resistance to crizotinib invariably develops, however, through a variety of mechanisms. In the last few years, a flurry of new and more potent ALK inhibitors has emerged for the treatment of ALK-positive NSCLC, including ceritinib (LDK378), alectinib (RO5424802/CH5424802), AP26113, ASP3026, TSR-011, PF-06463922, RXDX-101, X-396, and CEP-37440. Cancers harboring ALK rearrangements may also be susceptible to treatment with heat shock protein 90 inhibitors. This review focuses on the pharmacologic and clinical properties of these compounds, either as monotherapies or in combination with other drugs. With so many ALK inhibitors in development, the challenges of how these agents should be studied and ultimately prescribed are also discussed.