The purchaser-provider split within the NHS which emerged out of the government's 1990 White Paper, Working for Patients, together with the introduction of the Patients Charter, has imposed new, tighter performance measures on provider units. The internal market has placed clear contractual guarantees on providers in terms of service/care provided. The Patients Charter has set, with little reference to local conditions, required timescales for treatment, i.e. waiting time guarantees for patients. The government is committed to reducing these guaranteed waiting times further. Both these factors have forced provider units to look far more closely at the way they operate, and the way they provide services. The impact of these performance measures has been magnified by the tight budgetary constraints within which provider units are currently expected to operate. Consequently the option of increasing service provision through expanding facilities and staff has effectively been precluded in the majority of instances. Thus provider units have been forced into reappraising the manner in which service provision is structured and the services delivered. While this restructuring of service provision has been most obvious in those services where the internal market has had the more immediate effect - for example, direct access services such as physiotherapy - increasingly, performance measure pressures have forced providers to examine the processes by which they deliver both in-patient and out-patient care. Analyses the difficulties encountered by an NHS Trust in Scotland in managing capacity and demand in a specialist out-patient clinic.