The National Institute for Health and Clinical Excellence (NICE) produces guidance on the use of new and existing medicines, treatments and procedures within the NHS, including the efficacy and safety of interventional procedures. This guide describes the principles and methods used to assess interventional procedures. The methods are designed to ensure that robust guidance for the NHS is developed in an open, transparent and timely way that allows appropriate input from consultees and other stakeholders. This guide is intended to be complementary to the ‘Interventional Procedures Programme manual’ (‘IP Programme manual’).