63 Assessing medical decision-making competence in transgender minors 4 making well-considered decisions and that minors from the age of nine years are capable of understanding the issues involved in clinical trials (Billick, Edwards, Burgert, & Bruni, 1998; Mårtenson & Fägerskiöld, 2008). Contributing factors for MDC are intelligence and psychological functioning (Dorn et al., 1995; Grisso, & Appelbaum, 1998). People with limited cognitive capacities may have more difficulty understanding information (Grisso, & Appelbaum, 1998). Research suggests that psychiatric conditions and psychopathology might impair MDC (Cairns et al., 2005; Owen et al., 2008; Palmer et al., 2005). Little research exists regarding minors’ MDC (Hein et al., 2015d). Specifically, there is no empirical evidence on transgender adolescents’ MDC to decide on PS. In clinical practice and policy making, age standards prescribed by law may have too much influence on the clinicians’ assessments (Hein et al., 2015d). In addition, clinicians’ assessments of MDC are influenced by their personal subjective views of what is in the adolescent’s best interest (de Vries, Wit, Engberts, Kaspers, & van Leeuwen, 2010). The right balance needs to be struck between respecting transgender adolescents’ autonomy and protecting adolescents who are not fully capable of making these decisions themselves (Appelbaum, 2007). To fill the gaps in knowledge regarding transgender adolescents’ MDC, in this crosssectional semistructured interview study, we aimed to answer the following questions: 1. Are transgender adolescents competent to give IC for starting PS, according to the standard IC procedure and the MacCAT-T? 2. What is the intermethod agreement between MDC judgements based on the standard IC procedure and the MacCAT-T? 3. What is the interrater agreement regarding MDC judgements between raters using the standard IC procedure and the MacCAT-T? 4. To what extent are age, intelligence, psychological functioning, duration of the diagnostic trajectory, sex, and family situation associated with transgender adolescents’ MDC regarding starting PS? METHODS Participants Participants were transgender adolescents visiting the Centre of Expertise on Gender Dysphoria of the Amsterdam University Medical Centres, Location VUmc in Amsterdam, the Netherlands, between January 1, 2016, and December 31, 2017, or visiting the genderidentity clinic of Leiden University Medical Centre, Leiden University Medical Centre Curium, in Leiden, the Netherlands, between March 1, 2017, and December 31, 2017. The researchers identified the adolescents who were about to start PS through the medical