Despite mounting public, governmental and corporate interest in issues of non-governmental organisation (NGO) accountability, there are few academic studies investigating the emergence of accountability mechanisms in specific advocacy NGO settings. Drawing on the theoretical constructs of hierarchical and holistic accountability, this paper addresses this research gap by investigating recent developments in accountability practices at the Irish section of the human rights advocacy NGO Amnesty International. Through analysis of a series of in-depth interviews with managers in Amnesty Ireland, supported by extensive documentary scrutiny, this study examines reasons why Amnesty's historical reliance on internal forms of accountability has been augmented with a range of ad hoc external accountability mechanisms. The study reveals that while managers favoured the development of holistic accountability mechanisms exhibiting accountability to a wide range of stakeholders, a hierarchical conception of accountability privileging a narrow range of (potentially) powerful stakeholders, has begun to dominate external accountability discourse and practice. It was widely perceived that this trend could, somewhat paradoxically, prove counterproductive to the achievement of Amnesty's mission. Resolving this paradox will, at a minimum, involve Amnesty Ireland's leadership becoming more open to and more knowledgeable about a broader, more holistic accountability conception. The paper considers the possible implications of these findings for the development of NGO holistic accountability practice more generally. © 2008 Elsevier Ltd. All rights reserved.