Few empirical studies have examined how performance measures change in practice and the driving forces behind this change. The existing body of literature has taken a prescriptive approach to how managers and organisations ought to manage change in performance measures without any concern for studying the phenomenon itself and thus a theoretical gap exists. With this gap in mind, the purpose of this paper is to outline how and why the performance measures have changed at two case companies over the time period 2008-2011. In order to fulfil the purpose of this paper two case studies at two different case companies have been conducted. The choice of data collection method is justified by the ambition to attain an in-depth and holistic understanding of the phenomenon. For each case, the data collection was based on four components: an interview study, analysis of archived data, documentation and direct observations. In total, 28 interviews were conducted, 14 at each case company. The empirical findings exhibit that the performance measures are exposed to continuous and considerable change from several perspectives. The measurement scopes at both case companies are steadily expanding, the individual performance measures are constantly replaced and their characteristics are continuously altered. An array of change triggers has been identified in the empirical findings. In contrast to what is advocated in literature, the findings illustrate that the most frequent reason for change is the will to improve the performance measures, the measurement process and the overall performance rather than changing internal and external environments. There are several challenges that need to be addressed in the future research agenda.