When health service managers in Nottingham planned to move much of their outpatient activity to a proposed Diagnosis and Treatment Centre (DTC) they welcomed the opportunity to re-design the delivery of these services in a new setting. However, the lack of accessible, detailed information about outpatients' resource requirements posed an initial problem. Numerous, separate information systems offered diverse data: these were validated and assimilated into a single model of outpatient requirements. Discussions with staff and examples of innovative practice in other hospitals were investigated to develop an understanding of the implications of re-design for resources and capacity planning. The result was a high level outpatient planning model which could estimate the outpatients' requirements for related services such as radiology, therapies, pathology, endoscopy, cardiology tests, pharmacy and even patient transport. The model was developed as a decision support tool for managers examining a range of options for the Diagnosis and Treatment Centre allowing them to explore the effects of assumptions about future demand and changing practice in the delivery of healthcare.