ROS1 rearrangements are even less common than ALK translocations, but the results of this initial experience suggest a similar response pattern in that 8 of 14 evaluable patients experienced objective tumor responses to crizotinib. This has effectively identified ROS1 as the third mutation in NSCLC that is currently targetable, and it provides the impetus for more widespread FISH testing, particularly for nonsmokers without EGFR mutations or ALK translocations.