Parliamentary strengthening involves trade-offs, both in the choice between issue-based and institutional approaches, and in the choice of who a programme will include. Democracy promoters cannot avoid these trade-offs, but with systematic evaluation of past programmes they can navigate them more effectively. This policy paper draws on the Westminster Foundation for Democracy’s experience in parliamentary strengthening to suggest how this might be done. In doing so it demonstrates the utility of greater collaboration between academic researchers and democracy promoters. It also illustrates the gains that can be made when those who undertake parliamentary strengthening make their experience public knowledge.