OBJECTIVES: The expected value of perfect information (EVPI) assesses, at a given willingness-to-pay threshold, the expected gain in net benefit from further research to decrease uncertainty in a decision. If the EVPI exceeds the cost of obtaining new information then further research is considered valuable. The parameters for which further research is believed to be most valuable can be assessed by calculating the expected value of perfect parameter information. The objective of this analysis was to assess the use of EVPI in economic evaluations and health technology assessment (HTA) from the perspective of the NHS in the UK. METHODS: An unrestricted search was performed in MEDLINE for literature that contained references to EVPI and cost-effectiveness analysis or HTA. The literature obtained was assessed to establish the extent to which EVPI is used in economic evaluation and HTA. Guidelines from the National Institute for Health and Clinical Excellence (NICE) were also checked for references to EVPI. RESULTS: The literature search indicated that out of 73,795 results for HTA or cost-effectiveness analysis, only 70 (<0.01%) of these also reported EVPI. There were 21 examples of calculating the EVPI in an economic evaluation from a UK perspective; the earliest was published in 2004. The NICE guide to the methods of technology appraisal (2008 update) states that value-of-information methods can be used within a probabilistic sensitivity analysis (PSA) to assess the contribution of uncertainty from each parameter to the overall decision uncertainty. However, the specification for manufacturer/sponsor submission of evidence does not explicitly request the EVPI to be calculated as part of the PSA. CONCLUSION: The EVPI is a measure which can aid decision makers by quantifying the value of further research in an area, but it is not widely reported in published economic evaluations.