BackgroundAlcoholics Anonymous (AA) is a world-wide recovery mutual-help organization that continues to arouse controversy. In large part, concerns persist because of AA's ostensibly quasi-religious/spiritual orientation and emphasis. In 1990 the United States' Institute of Medicine called for more studies on AA's effectiveness and its mechanisms of behavior change (MOBC) stimulating a flurry of federally funded research. This paper reviews the religious/spiritual origins of AA and its program and contrasts its theory with findings from this latest research. MethodLiterature review, summary and synthesis of studies examining AA's MOBC. ResultsWhile AA's original main text (the Big Book', 1939) purports that recovery is achieved through quasi-religious/spiritual means (spiritual awakening'), findings from studies on MOBC suggest this may be true only for a minority of participants with high addiction severity. AA's beneficial effects seem to be carried predominantly by social, cognitive and affective mechanisms. These mechanisms are more aligned with the experiences reported by AA's own larger and more diverse membership as detailed in its later social, cognitive and behaviorally oriented publications (e.g. Living Sober, 1975) written when AA membership numbered more than a million men and women. ConclusionsAlcoholics Anonymous appears to be an effective clinical and public health ally that aids addiction recovery through its ability to mobilize therapeutic mechanisms similar to those mobilized in formal treatment, but is able to do this for free over the long term in the communities in which people live.