This discussion document aims to provide guidance to those thinking of initiating policy pilots and commissioning or requesting others to commission their evaluations. It addresses a number of issues that are specific to policy piloting and that need to be considered before selecting pilot sites and commissioning evaluation. Much advice on evaluation today is focused on advocating the adoption of specific study designs – especially randomised controlled trial (RCTs). While RCTs will be relevant to consider for specific purposes, as we discuss below, they may well not be the best option for the evaluation of policy pilots. We therefore aim to encourage consideration of a range of evaluation designs so as to capitalise fully on the opportunities for learning from policy piloting but, more importantly, to encourage more thinking about other aspects of commissioning evaluations of policy pilots. The advice is primarily designed for national level staff involved in policy making, programme management, monitoring and analysis, and responsible for initiating policy-relevant pilots and commissioning their evaluations.