This paper describes the methods used in economic evaluation and illustrates the challenges of assessing the cost-effectiveness of new interventions in Hepatitis C (HCV), where the impact of interventions needs to be assessed over the patient's lifetime. This paper provides an example of an economic evaluation in HCV using a model estimating the cost-effectiveness of combination therapy (CMB) for patients with mild HCV. The preliminary results from the model suggested that for 1000 cases with mild disease CMB lead to 55 fewer deaths from liver disease compared to no treatment, an average gain of 1.2 life years. Although CMB lead to additional costs of 14,882 EURO's, the cost-effectiveness ratio was 8,490 EURO's per Quality Adjusted Life Year (QALY), which suggests the intervention is relatively cost-effective. The sensitivity analysis showed that the cost-effectiveness ratio was sensitive to the effectiveness of the intervention, and the progression rates between mild disease and cirrhosis. A large UK study is collecting data on the effectiveness of CMB for patients with mild disease, and the costs and quality of life for patients at different stages of HCV. These data will be used to improve the projections of the model. In general, economic evaluations can provide information to help decide where priorities lie both in HCV, and other disease areas.