Background and aims: Although the National Institute of Health and Clinical Excellence (NICE) mandates service user involvement in developing treatment guidelines, questions arise concerning appropriate mechanisms of involvement and its impact. This study sought to elicit users' perceptions of their involvement.
Method: Grounded theory was used to analyse transcripts from interviews with 10 service user guideline development group representatives.
Results: Four categories emerged suggesting that participants drew upon expertise developed through experience and impact upon the process and product of guideline development. Unwritten rules and social comparisons influence deliberations.
Conclusions: Service users reported making a useful contribution despite intrinsic barriers.