The objective of the present study was to determine whether provision of health advocacy for homeless patients would reduce the burden of care for a primary healthcare team. The impact of a health advocacy intervention was assessed in a quasi-experimental, three-armed controlled trial. Homeless patients registering at an inner-city health centre were allocated in alternating periods to health advocacy (with or without outreach registration) or 'usual care' over a total intake period of 3 years. The client group were homeless people in hostels or other temporary accommodation in the Liverpool 8 area of the UK. The majority of participants (n = 400) were women (76%) in their twenties (mean age = 26.6 years). Most (63%) were temporarily housed at either one of the women's refuges or Liverpool City Council family hostels, and all were registered with an inner-city health centre. Data on health service utilisation over a 3-month period was collected for all clients recruited to the study and direct health service costs were measured. Homeless adults who were proactively registered by the health advocate on outreach visits to hostels made significantly less use of health centre resources whilst having more contact with the health advocate than patients who registered at the health centre at a time of need. There was no reduction in health centre workload when the offer of health advocacy was made after registration at the health centre. The additional costs of providing health advocacy were offset by a reduction in demand for health-centre-based care. The results demonstrate that health advocacy can alter the pattern of help-seeking by temporarily homeless adults. The intervention was cost-neutral. The short-term health service workload associated with symptomatic homeless patients requiring medication was not reduced, but outreach health advocacy was used successfully to address psycho-social issues and reduce the workload for primary care staff.