This study examined the relationships between participation in professional treatment and Alcoholics Anonymous (AA) among 473 initially untreated individuals with alcohol use disorders. These individuals were assessed at baseline and at 1-year, 3-year, and 8-year followups. There were moderate positive concurrent associations between the duration of participation in professional treatment and in AA. More important, a longer duration of treatment in year 1 was associated with more sustained participation in AA in years 2 and 3, which was associated with less time in treatment in years 4 through 8. The strength of these findings varied somewhat in relation to whether individuals chose to enter treatment or AA first. The findings suggest that referral and alliance processes contribute to a positive association between the duration of an initial episode of treatment and subsequent AA, and then extended participation in AA contributes to better alcohol-related outcomes and reduced need for subsequent treatment.