Childhood genetic testing raises complex ethical and moral dilemmas for both families and professionals. In the family sphere, the role of communication is a key aspect in the transmission of 'genetic responsibility' between adults and children. In the professional sphere, genetic responsibility is an interactional accomplishment emerging from the sometimes competing views over what constitutes the 'best interests' of the child in relation to parental preferences on the one hand, and professional judgements on the other. In the present paper we extend our previous research into parental accounts of childhood genetic testing and explore the ethical accounts of professionals in research interviews. Interviews (n = 20) were conducted with professional practitioners involved in the genetic diagnosis and management of children and their families. We first identify four inter-related themes-juxtaposition of parental rights vis-à-vis child's autonomy, elicitation of the child's autonomy, avoidance of parental responsibility and recognition of professional uncertainty. Then, using Rhetorical Discourse Analysis, we examine the range of discourse devices through which ethical accounts are situationally illustrated: contrast, reported speech, constructed dialogue, character and event work. An overarching device in these ethical accounts is the use of extreme case scenarios, which reconstruct dilemmas as justifications of professional conduct. While acknowledging ambivalence, our analysis suggests that professional judgement is not a simple matter of implementing ethical principles but rather of managing the practical conditions and consequences of interactions with parents and children. We conclude that more attention is needed to understand the way professional practitioners formulate judgements about ethical practice.