This article provides an account of the impact of Constance Hanf, Ph.D., developer of the well-known two-stage parent training model that bears her name. Past colleagues, interns, postdoctoral students, and undergraduate trainees reflect on their experiences with Dr. Hanf and comment on her influence on their careers, as well as the impact of the model on child behavior therapy. The paper first briefly describes child therapy as it existed before the advent of behavioral parent training, and subsequently describes Dr. Hanf's parent training model and career. Finally, we attempt to elucidate the personal side and professional impact of this very important figure in contemporary empirically based work with families. (Contains 2 tables and 1 figure.)