Objective: To determine which aspects of open disclosure "work" for patients and health care staff, based on an evaluation of the National Open Disclosure Pilot. Design, setting and participants: Qualitative analysis of semi-structured and open-ended interviews conducted between March and October 2007 with 131 clinical staff and 23 patients and family members who had participated in one or more open disclosure meetings. 21 of 40 pilot hospital sites, in New South Wales, South Australia, Victoria and Queensland, were included in the evaluation. Participating health care staff comprised 49 doctors, 20 nurses, and 62 managerial and support staff. In-depth qualitative data analysis involved mapping of discursive themes and subthemes across the interview transcripts. Results: Interviewees broadly supported open disclosure; they expressed uncertainty about its deployment and consequences, and made detailed suggestions of ways to optimise the experience, including careful pre-planning, participation by senior medical staff, and attentiveness to consumers' experience of the adverse event. Conclusion: Despite some uncertainties, the national evaluation indicates strong support for open disclosure from both health care staff and consumers, as well as a need to resource this new practice.