Objective: Our aim was to examine the reliability and validity of the Rupture Resolution Rating System (3RS), an observer-based measure of alliance ruptures and resolution processes. Method: We used the 3RS to rate early sessions from 42 cases of cognitive behavior therapy. We compared the 3RS to a simplified version of the Structural Analysis of Social Behavior (SASB), as well as patient and therapist self-reports of ruptures and the alliance. Results: Coders achieved high rates of interrater reliability on the frequency of confrontation and withdrawal ruptures and resolution strategies (ICCs=.85 to .98), as well as ratings of the therapist's contribution to ruptures and the extent to which ruptures were resolved (ICC=.92). Predictive validity analyses found that confrontation markers (d=.74), successful resolution (d=. 67), and ratings of the therapist's contribution to ruptures (d=.61) predicted dropout from therapy. Analyses of convergent validity with the SASB failed to meet predictions; however, we observed theoretically coherent relations between 3RS and SASB variables. Confrontation rupture markers were significantly associated with patient self-report of rupture (d=1.54) and therapist selfreported alliance (r = −.50, p = .002). Conclusions: This study provides evidence that the 3RS is a reliable and useful tool for examining psychotherapy process and predicting dropout.