Personal Medical Services (PMS) contracts, introduced in 1997, provide a new financial model for providing general practice. The aim of this study was to measure the costs and consequences of the PMS first wave contracts for sites that aimed to increase the accessibility and the quality of care for vulnerable population groups; to describe the problems encountered in this measurement. A purposive sample of first wave PMS sites targeting vulnerable population groups were selected. A two-stage data collection procedure was used, to obtain micro-level data on the quantity and costs of capital and recurrent funds, and top-down data on costs and apportioning of monies received from central source to broad expenditure categories. The costs data focused on the largest cost components, such as staff and prescribing as well as alternative stakeholders’ contributions. The consequences data measured the accessibility and the quality of care for vulnerable population groups. Five case studies were considered. Sites that were formerly independent general medical practitioner (GP) contractors consolidated their staff with few changes in their staff-skill mix. In all sites the prescribing costs per patient were below the national average in 2000/01. Access was either consolidated or improved over the period and improved quality of care was in evidence through appropriate prescribing patterns. Though the evaluation found that the PMS sites were addressing their main objectives the data collection revealed difficulties in tracking the flows of PMS resources under the current budgetary system. We highlight the limitations of the PMS data monitoring procedures and discuss how these limitations can be overcome so that future National Health Services (NHS) reforms can be appropriately evaluated in the future.