Charismatic authority flourishes in places where some social scientists evidently do not expect to find it - in late modernity and in highly complex and instrumentally orientated technoscientific organizations. This paper documents and interprets participants' testimony about the workings of wartime Los Alamos in relation to the charisma of its Scientific Director. J. Robert Oppenheimer. We treat charisma as an interactional accomplishment, and examine its role in technoscientific organizations. Los Alamos was a hybrid place, positioned at the intersection of military, industrial and academic forms. Everyday life there was marked by a high degree of normative uncertainty. Structures of authority, communication and the division of labour were contested and unclear. The interactional constitution of Oppenheimer as charismatic enabled him to articulate, vouch for and, finally, come to embody a conception of legitimate organizational order as collegial, egalitarian and communicatively open. We offer concluding speculations about the continuing importance of charismatic authority in contemporary technoscientific organizations. Just as normative uncertainty is endemic in late modernity, so too, we argue, is charisma.