Examines the dynamics of change that operated following preparations for accreditation. The study was conducted from May 1995 to October 2001 in a university hospital center in France after the introduction in 1996 of mandatory accreditation. An embedded explanatory case study sought to explore the organizational changes: a theoretical framework for analyzing change was developed; semi-structured interviews, focus groups, and questionnaires addressed to the hospital's professionals were used and documents were collected; and qualitative and quantitative analyses were carried out. Professionals from clinical and medico-technical departments participated most. Preparations for accreditation provided an opportunity to reflect non-hierarchically on the treatment of patients and on the hospital's operational modalities by creating a locus for exchanges and collegial decision making. These preparations also led to giving greater consideration to results of exit surveys and to committing procedures to paper, and were a key opportunity for introducing a continuous quality program.