The landmark decision of Gillick v West Norfolk Area Health Authority was a victory for advocates of adolescent autonomy. It established a test by which the court could measure children's competence with a view to them authorising medical treatment. However, application of the test by clinicians reveals a number of ambiguities which are compounded by subsequent interpretation of Gillick in the law courts. What must be understood by minors in order for them to be deemed competent? At what point in the consent process should competence be assessed? Does competence confer on minors the authority to refuse as well as to accept medical treatment? These are questions which vex clinicians, minors and their families. A growing number of commentators favour application of parts of the Mental Capacity Act 2005 to minors. In this paper, the limitations of this approach are exposed and more radical reform is proposed.