The general issue of balancing the value of evidence about the performance of a technology and the value of access to a technology can be seen as central to a number of policy questions. Establishing the key principles of what assessments are needed, as well as how they should be made, will enable them to be addressed in an explicit and transparent manner. The aims of this research are to: i) Establish the key principles of what assessments are needed to inform an only in research (OIR) or Approval with Evidence Development (AED) recommendation. ii) Evaluate previous NICE guidance where OIR or AED recommendations were made or considered. iii) Establish what impact OIR and AED decisions may have had on subsequent research. iv) Evaluate a range of alternative options to establish the criteria, additional information and/or analysis which could be made available to help the assessment needed to inform an OIR or AED recommendation. v) Provide a series of final recommendations, with the involvement of key stakeholders, establishing both the key principles and associated criteria that might guide OIR and AED recommendations, identifying what, if any, additional information or analysis might be included in the Technology Appraisal process and how such recommendations might be more likely to be implemented through publically funded and sponsored research. To meet these aims the research is broadly structured as follows: i) development of a coherent conceptual framework to establish the key principles of what assessments need to be made and identify a set of explicit criteria (checklist of assessments) which could be applied; ii) review previous NICE guidance and develop a series of detailed case studies to evaluate a range of options for informing these assessments; iii) evaluate both the development of key principles and the range of options for informing assessments through a series of workshops involving a wide range of key stakeholders.