Although recent research has investigated the attitudes of parents, professionals, and adult siblings toward carrier testing of minors, no studies have focused on the experiences of minor siblings of individuals with X-linked and autosomal recessive conditions. To explore adolescent sisters' perceptions of their reproductive risks, attitudes toward carrier testing, and resources for information and support, we interviewed 14 parents and 9 sisters (ages 12–15) of males with chronic granulomatous disease (CGD), a primary immunodeficiency disorder inherited in both an X-linked recessive and autosomal recessive fashion. Our semistructured telephone interviews were audiotaped, transcribed, and subjected to template analysis (a common qualitative methodology). Girls were all aware that CGD is an inherited condition and each had made an assessment of her reproductive risk. All girls considered their parents to be their best source of information and support, but girls had trouble initiating discussions for fear of upsetting their parents. All girls and parents considered eventual carrier testing vital for reproductive decision-making and relationship-building. However, girls favored carrier testing at a later age and expressed more concerns about psychological risks associated with testing than did their parents. When faced with the hypothetical situation of being offered carrier testing “tomorrow,” half of the parents and untested daughters disagreed on the desirability of the test, with parents more likely to favor testing. Including adolescent sisters in family-based genetic counseling that provides an opportunity for age-appropriate discussion of inheritance and the timing, risks, and benefits of carrier testing would be beneficial to them. Published 2003 Wiley-Liss, Inc.