The predictive validity of instruments commonly used to measure the therapeutic alliance was evaluated, using 46 sessions drawn from a clinical trial comparing manual-guided therapies for substance use. The California Psychotherapy Alliance Scale, Penn Helping Alliance Rating Scale, Vanderbilt Therapeutic Alliance Scale, and Working Alliance Inventory (Observer, Therapist, and Client versions) were rated for participants receiving either cognitive-behavioral therapy or twelve-step facilitation. All observer-rated instruments were significantly correlated with outcome; however, therapist-rated and client-rated instruments did not predict outcome. Findings suggest that the different observer-rated instruments are minimally different with respect to predictive validity, whereas patient- and therapist-rated measures may have a weaker relationship to outcome when highly objective outcome measures are used.