We argue that contemporary research on the influence of organisational autonomy on performance in public organisations uses a diverse and a too restrictive conceptualisation of autonomy. After discussing that research, the article develops six dimensions of the concept of autonomy in public organisations. Second, weaknesses of contemporary research are shown by confronting their conceptualisations with the developed taxonomy. Third, data from a survey of Flemish public organisations illuminate the need to acknowledge the six different dimensions of autonomy when studying the effect of autonomy on performance. The empirical material points at the dangers of using formal–legal status of a public organisation as an indicator of its autonomy, given substantial heterogeneity of organisations with the same formal–legal status on each dimension of autonomy. Moreover, tensions between different levels of autonomy appear in practice, indicating the need for a combined and integrated study of the effects of the different dimensions of autonomy on performance. Copyright © 2004 John Wiley & Sons, Ltd.