Background: Schools can address critical sexual and reproductive health (SRH) issues among youth. However, little is known about SRH education being implemented in charter schools. Thus, our purpose was to explore implementation of SRH education in charter schools. Methods: Using purposive sampling, semistructured telephone interviews were conducted with 20 charter school principals in San Diego County, California. Questions were guided by the Kaiser Family Foundation National Survey of Public Secondary School Principals. Analyses followed a case-oriented approach, examining aspects within each case (ie, a principal), and then a comparative analysis of a small number of cases (ie, all principals). Results: Overall, 17 principals acknowledged offering sexuality education in the previous 2 years. Over half of these schools had provided content on: sexually transmitted diseases/human immunodeficiency virus/acquired immune deficiency syndrome (STDs/HIV/AIDS), reproduction/pregnancy/birth, pregnancy prevention methods, delaying sex, and managing sexual pressure. Condom use, sexual assault, sexual orientation, talking with partners about STD/pregnancy prevention, talking with parents about relationships/sex, and using/where to get contraception were less commonly taught. Abortion was not addressed. When asked the grade they would assign to their schools' sexuality/HIV instruction, principals assigned 1 A, 7 Bs, 7 Cs, and 1 D. Conclusions: Consistency between our findings and what has been reported elsewhere varies. As charter schools often have greater curricular flexibility than traditional schools, this study provides unique preliminary data to inform future innovative, or strengthen existing, SRH programming.