Introduction:  Previous impact tool-kits for UK health libraries required updating to reflect recent evidence and changes in library services. The National Knowledge Service funded development of updated guidance.

Methods:  Survey tools were developed based on previous impact studies and a systematic review. The resulting draft questionnaire survey was tested at four sites, and the interview schedule was investigated in a fifth area. A literature search in assia, Google Scholar, intute, lisa, lista, scirus, Social Sciences Citation Index (Web of Knowledge), and the major UK University and National Libraries Catalogue (copac), identified ways to improve response rates. Other expert advice contributed to the guidance.

Results:  The resulting guidance contains evidence-based advice and a planning pathway for conducting an impact survey as a service audit. The survey tools (critical incident questionnaire and interview schedule) are available online. The evidence-based advice recommends personalizing the request, assuring confidentiality, and using follow-up reminders. Questionnaires should be brief, and small incentives, such as a lottery draw should be considered. Bias is minimized if the survey is conducted and analysed by independent researchers.

Conclusion:  The guidance is a starting point for a pragmatic survey to assess the impact of health library services.