Assimilative integration is a new type of psychotherapy integration introduced by Messer in 1992. This paper explains the "where , what, when, and how" of this integrative route, outlines its advantages and weaknesses, and discusses areas for potential assimilative practice in various models of therapy. Following a brief review of the current status of psychotherapy integration and its practices, assimilative integration is conceptualized as a "mini theoretical integration" and as "theoretical eclecticism"; it is offered as a bridge between theoretical integration and technical eclecticism. Assimilative integration is proposed as the best theoretically and empirically based integrative approach available at this time, particularly for therapists who have been trained in a single mode of therapy before they became integrationists.