Sex/HIV education curricula have disparate effects for females and males. Review of 59 rigorous sex ed evaluations from the U.S. and developing countries. After omitting single sex programs, programs with no effect, and programs that changed only knowledge, 38 remained (25 U.S. and 13 developing country). A third of these failed to disaggregate results by gender, leaving 25. This article looks at why this is the case and how gender affects SRH outcomes.