The use of accreditation has been widespread among medical care providers, but accreditation is relatively new to the drug abuse treatment field. This study presents estimates of the costs of pursuing accreditation for methadone treatment sites. Data are from 102 methadone treatment sites that underwent accreditation as part of the Center for Substance Abuse Treatment's evaluation of the Opioid Treatment Program Accreditation Project. The analysis represents the most comprehensive analysis of the costs of pursuing accreditation by a health care provider. Importantly, it is the first analysis of the costs of pursuing accreditation by drug treatment providers. Policy makers and drug treatment providers can use this analysis to plan the labor requirements and costs of future accreditation initiatives. (Contains 6 tables, 2 figures, and 3 notes.)