The paper describes how Hospital Episode Statistics (HES) data can be retrospectively analysed over a number of years to evaluate and monitor organizational change in National Health Service (NHS) trusts. A methodology based on joinpoint regression analysis and management control theory has been developed which is able to represent in a framework (called an 'activity map') the complexity of HES data in a more user-friendly way than the unwieldy and often overwhelming tables or spreadsheets that are typically utilized. The 'activity map' has been designed to provide a common frame of reference for health professionals from different backgrounds to visualize and interpret the actual patterns of hospital activity changes that have occurred over the years. The aim is to facilitate a more effective, faster and more intuitive exploration of very large and unwieldy HES data-sets to assist health-care staff in monitoring planned and unplanned activity changes. It is hoped that making HES data more easily assimilated will encourage a greater sense of meaningful engagement in creatively contributing to service innovation.