Starting from early conceptions of the therapeutic alliance, the development of the construct is traced. Our thesis is that its attractiveness for psychotherapy research is mainly due to its relationship to therapy outcome. There are, however, also critical comments from researchers, who consider the mainstream perspective as too positivistic. Considering them from a research point of view, different approaches are reflected, which summarize the results concerning the therapeutic alliance as a patient or therapist-oriented personality variable or rather as an interactional or communication variable. It is attempted to describe the impact of the therapeutic alliance in different forms and settings of therapy. Frequently used scales are described, including the results with regard to their similarity. Statements about the course of alliance over therapy and about potentially typical processes, which are based on results achieved by these scales, are discussed. As the therapeutic alliance originally stems from psychoanalysis and its relationship to transference evoked repeated discussions in the literature, this aspect is also focused on in this report.