Over the past decade, the Gurian Institute has trained more than forty thousand teachers in more than two thousand schools and districts, both coed and single-sex. The institute's trainers have worked with public and private schools, Montessori schools, and a variety of charter and independent schools in fifteen countries; it has therefore been able to see what is working and not working around the globe. In this essay, the authors feature some of the schools and communities that have utilized Gurian Institute's resources to help set up and maintain successful single-sex programs. The authors provide a short history of the "new" single-sex option and discuss different approaches and success data from a variety of schools. Some examples of success in the different single-sex modalities are presented.