The stormier the sea the harder it is to steer between the Cylla of mission drift and the Charybdis of obsessive measurement disorder. Rigorous impact assessment can be both lauded as an antidote to biased and wishful thinking, and attacked for diverting attention from more important but harder-to-measure goals. The seminar will explore this tension in relation to international development practice through reflections on action research designing and mainstreaming a qualitative impact protocol (the ‘QuIP’). This aims to generate credible evidence of how a specified intervention contributes to intended and unintended outcomes in a way that is relatively inexpensive, scale-neutral, flexible and quick. There is progress to report in addressing potential confirmation and case selection biases. But many challenges remain and will also be discussed. The seminar draws on “Attributing Development Impact”, available as a free e-book at bit.ly/QuIP-OA.