Strengthening the accountability and improving the performance of public services is an important issue in many countries. A common response is to impose elaborate oversight or scrutiny arrangements. While we know a good deal about the formal operation of these arrangements, we know much less about the informal practices of scrutiny bodies and how they make judgements. This paper investigates scrutiny processes in three national audit bodies, three service inspectorates, and two inquiry committees in the UK. Judgement processes were analyzed along five dimensions: intuitive to analytical thinking; implicit to explicit assessment criteria; inductive and deductive methods; internal and external validity; and the principles used to make and evaluate judgements. These processes varied considerably, suggesting the need for a broader conception of the nature of and influences on scrutiny processes, which recognizes the inherent tensions in these processes and the skills required by those who engage in them.