This chapter reviews the history and definition of countertransference, as well as empirical research on countertransference, its management, and the relation of both to psychotherapy outcome. Three meta-analyses are presented, as well as studies that illustrate findings from the meta-analyses. The first meta-analysis indicated that countertransference reactions are related inversely and modestly to psychotherapy outcomes (r = –.16, d = –.33, k = 14 studies, N = 973). A second meta-analysis supported the notion that countertransference management factors attenuate countertransference reactions (r = –.27, d = –.55, k = 13 studies, N = 1,065). The final meta-analysis revealed that successful countertransference management is related to better therapy outcomes (r = .39, d = .84, k = 9 studies, N = 392 participants). The authors conclude by summarizing the limitations of the research base, noting diversity considerations, and highlighting the therapeutic practices predicated on research.