Billions of dollars are spent annually on humanitarian support to households in crisis. Researchers discuss a large-scale evaluation that tests the impact of anticipatory cash transfers in response to floods in Bangladesh. Humanitarian workers carry out incredible lifesaving work every day on the front line of crisis response to assist those in the greatest need. Yet repeatedly, despite the fact that billions of dollars are spent annually on humanitarian support to households in crisis, there is very limited evidence on the impact of this support. This project is one of the first large-scale evaluations that rigorously tests the impact of humanitarian cash transfers in response to a sudden extreme weather event, and the importance of being timely for an impactful response. Creative Commons Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales; http://creativecommons.org/licenses/by-nc-sa/2.0/uk/