Participation in the Australian Council on Hospital Standards' accreditation program provides one of the important stimuli for change in Australian hospitals. This article analyses the impact of the accreditation program upon a random sample of 23 Australian hospitals which were monitored for two years. At the conclusion of the study, those hospitals which had applied for accreditation were compared and contrasted with those hospitals which had not applied. It was found that those hospitals which applied could be differentiated from those hospitals which had not by significant changes in six areas. The areas which showed the least change were those most directly associated with the medical staff. 'Nursing Organisation' and 'Physical Facilities and Safety' were the areas most affected by accreditation.