For more than three decades, gender-responsive programs have been part of the landscape of services provided to women and girls in, or at risk of entering, a justice system traditionally geared toward males. These single-sex programs — born out of research showing that girls’ risk factors and pathways into the justice system are different from boys’ — focus on girls’ unique needs and strengths. But while policies at the state and national levels support such services, research on their components and their effectiveness is limited. This brief describes the principles of gender-responsive programs, summarizes the literature, and presents highlights of MDRC’s implementation study of PACE Center for Girls. The PACE evaluation offers an important opportunity to describe how gender-responsive principles are put into operation in a real-world setting — across 14 locations in Florida — and to investigate the effects on girls’ lives.