ABSTRACT. Objective: Pre-post changes in readiness for change (RC) are commonly assessed in treatment outcome studies, often with contradictory results. Little is known about 12-month RC trajectories among those initiating change or about the association between RC and either within-or between-person alcohol use or time-lagged help-seeking behavior. Method: This observational longitudinal study measured RC as ambivalence, problem recognition, and taking steps. Participants (N = 253; 66.4% male) diagnosed with alcohol use disorders were recruited from treatment sites, Alcoholics Anonymous (AA) groups, and other community sources when fi rst initiating change and assessed at baseline and 3, 6, 9, and 12 months. Results: Support for signifi cant participant heterogeneity as well as linear and quadratic change in RC trajectories was found, although results differed across the three aspects of RC. Independent associations of both within-and between-person percentage of days abstinent were found for ambivalence and taking steps. Lagged, time-specifi c fl uctuations in prior help-seeking behaviors within an individual predicting subsequent RC showed that both AA (B = -1.650, p < .05) and treatment attendance (B = 2.914, p < .01) were associated with subsequent ambivalence. Prior increases in taking steps within individuals were predictive of subsequent AA but not treatment attendance. Conclusions: Results inform treatment providers about how RC trajectories vary depending on alcohol use, both within and between individuals, and how individuals may mobilize change attitudes and behaviors, especially in relation to AA attendance. Future research should investigate additional predictors of RC trajectories and the causal direction between RC and help seeking. (J. Stud. Alcohol Drugs, 75, 486-495, 2014)