Purpose: The purpose of this study was to identify and analyze research into accreditation and accreditation processes. Data sources: A multi-method, systematic review of the accreditation literature was conducted from March to May 2007. The search identified articles researching accreditation. Discussion or commentary pieces were excluded. Study selection: From the initial identification of over 3000 abstracts, 66 studies that met the search criteria by empirically examining accreditation were selected. Data extraction and results of data synthesis: The 66 studies were retrieved and analyzed. The results, examining the impact or effectiveness of accreditation, were classified into 10 categories: professions' attitudes to accreditation, promote change, organizational impact, financial impact, quality measures, program assessment, consumer views or patient satisfaction, public disclosure, professional development and surveyor issues. Results: The analysis reveals a complex picture. In two categories consistent findings were recorded: promote change and professional development. Inconsistent findings were identified in five categories: professions' attitudes to accreditation, organizational impact, financial impact, quality measures and program assessment. The remaining three categories - consumer views or patient satisfaction, public disclosure and surveyor issues - did not have sufficient studies to draw any conclusion. The search identified a number of national health care accreditation organizations engaged in research activities. Conclusion: The health care accreditation industry appears to be purposefully moving towards constructing the evidence to ground our understanding of accreditation.