INTRODUCTION The large numbers of 14 C dates obtained during the last fifteen years or so from excavations in Ireland have the potential to change fundamentally our understanding of Irish prehistory and early history.This is particularly the case for the Iron Age, where a lack of distinct site morphologies and finds assemblages (other than for high-status sites and metalwork) has previously hindered the identification of human activity (e.g. Raftery 1994; Armit 2007). Nevertheless, reliance on 14 C dates for the redefinition of archaeological periods also carries dangers that make awareness of the inherent issues and the critical interpretation of the individual dates crucial.This is a particularly pressing issue in Irish later prehistory, which is notoriously poor in associations with diagnostic finds, but it applies equally to other periods. This paper presents a methodology established in the project ‘Mobility, Culture and Climate: Remodelling the Irish Iron Age’ (MCC) for the evaluation of a dataset that will ultimately comprise more than 2,000 14 C dates (Armit et al., in prep.; Becker et al., in prep.). Following a pilot study (Becker 2009; Becker et al. 2008), all accessible 14 C dates from published and unpublished excavations were collected where the 2- sigma calibrated range impinges on the period 1200 BC–AD 400, i.e. covering the entire Irish late Bronze Age and Iron Age (Becker et al. 2010). A variety of issues affect the interpretation of radiocarbon dates. Some are inherent to the method, while others directly relate to sample selection and consequently interpretation.The distorting influence of the old wood effect, the problems inherent in dating mixed-entity samples, and the need to establish secure associations between 14 C samples and the features that they are intended to date have all been highlighted in previous studies (e.g. Ashmore 1999; Brindley 2007; Cleary 2007; Lanting and van der Plicht 1993–4;Warner 1990; 1997; Waterbolk 1971; Whittle et al. 2011). In order to assess the quality of Irish later prehistoric 14 C dates consistently and transparently, therefore, a grading scheme was devised that would take account of these and other issues potentially affecting the dataset. As well as providing an important step in the reinterpretations of the Irish Iron Age that form a key focus of the wider MCC project, this dating audit highlights a range of issues relating to the selection and use of 14 C dates in Irish archaeology that are of broader relevance to the discipline. THE GRADING SYSTEM The grading system devised for the MCC project assigns two separate grades to each date. The first is ‘sample quality’: broadly, this relates to the degree to which any given 14 C date can be taken to reflect the genuine time of the death of the sample. The second is ‘association quality’: essentially this relates to the degree of confidence with which a given 14 C date can be associated with some specific event that we might want to date, such as the building of a house or the filling of a pit. The reason for keeping these gradings separate is that they are conditioned by different factors, and some dates which fail spectacularly on one count may still be useful on another. For example, there may be occasions where we want to understand the spread and distribution of dated later prehistoric ‘events’ even where we cannot associate them confidently with any specific archaeological feature. In the following sections we outline the grading scheme and give both the general underlying principles and some examples to indicate how it has been applied. In an area as subjective as archaeology there will always be disagreements over interpretation, and we would not expect all archaeologists to agree with the inferences on which we have based our determinations of all specific cases. In this sense, any such grading system will be a blunt tool. Nonetheless, what is most important here is The Journal of Irish Archaeology Volume XX, 2011 19–25 Later prehistoric radiocarbon dates from Ireland: an audit K. Becker, 1 I. Armit, 1 J. Eogan 2 and G. Swindles 3 The evaluation and interpretation of radiocarbon dates in relation to clear research objectives is essential if they are to be utilised to their full potential. Both the quality of the material sampled and its archaeological association contribute to the overall quality of a date.This paper presents a grading scheme for the evaluation of radiocarbon dates and eval- uates the current quality of available dates relating to later prehistoric Ireland.