This article describes a theoretically based structural family assessment procedure designed for use in evaluating therapy outcome. The standardized procedure for eliciting family interaction consists of the administration of three family tasks. The family's interactional patterns on the tasks are evaluated along six dimensions of structural family functioning: Structure, Flexibility, Resonance, Developmental Stage, IdentifiedPatienthood, and Conflict Resolution. A manual has been developed for standardizing ratings for research applications. The measure demonstrated good interrater and internal consistency reliability. Available evidence for the content, factor, and construct validity of the measure is presented. Clinical outcome research studies conducted with the measure provide evidence that the measure is sensitive to different types of structural family intervention modalities and that it discriminates between a structural family intervention versus a no treatmentlwait list control condition as well as between a structural family intervention versus an individual psychotherapy treatment modality. Finally, the measure has been demonstrated to be nonreactive under both treatment and wait list conditions. For nearly two decades our program of research has focused on applying systems theory to what has emerged as a remarkably recalcitrant clinical problem, that is, Drs.