OBJECTIVES: There is expected to be an increase in the number of patients needing dialysis in the UK over the next 5 years. Outcomes for the different modalities available, haemodialysis (HD) and peritoneal dialysis (PD), have been shown to be similar yet the majority of dialysis patients are treated with HD. Any changes in dialysis delivery that could lead to a more efficient use of resources could increase the number of RRT patients that could be treated. The objective of this evaluation is to project a five-year impact on total dialysis costs when there is a hypothesised shift in modality from HD to PD. METHODS: An Excel-based budget impact model was used to estimate the impact of a shift in modality utilisation. The model takes into account dialysis modality shares, annual average cost of treating patients per modality, annual RRT growth rate and years to reach new modality distribution. Cost data from a recent UK study were used. At baseline (Jan 2007) there were 23,550 RRT patients undergoing dialysis therapy, 80% using HD and 20% using PD. Annual direct cost per patient was £35,023 for hospital HD, £32,669 for satellite HD, £20,764 for home HD (HHD), £21,655 for automated PD (APD), and £15,570 for continuous ambulatory PD (CAPD). Total costs included drug treatment and transport costs. At baseline, 2% of the HD population was on HHD and 40% of the PD population was on APD. RESULTS: If PD utilisation increases to 30% (of which 60% is APD) by 2012, the cumulative 5-year budget is reduced by £131 million. This savings can provide an additional 4,438 patient-years of treatment. CONCLUSIONS: In the UK, an increased use of PD provides an opportunity to treat additional patients within a fixed budget, which is a potential solution to the expected increased demand for RRT.