The National Institute for Health and Care Excellence (NICE) invited the manufacturer of daclatasvir (Bristol-Myers Squibb) to submit clinical and cost-effectiveness evidence for daclatasvir in combination with other medicinal products within its licensed indication for the treatment of chronic hepatitis C, as part of the Institute's single technology appraisal process. The Centre for Reviews and Dissemination and Centre for Health Economics at the University of York were commissioned to act as the independent Evidence Review Group (ERG). This article presents the ERG's critical review of the evidence presented in the company submission in the context of a description of the company submission, and the resulting NICE guidance. The main clinical effectiveness data for daclatasvir in combination with sofosbuvir (daclatasvir + sofosbuvir) were derived from two uncontrolled open-label trials. Among patients with genotype 1 infection, 98-100 % of patients had a sustained virologic response at week 12 (SVR12), overall. Among genotype 3 patients, between 85 and 100 % had SVR12 across patient populations and regimens. The main evidence for daclatasvir + pegylated interferon-α and ribavirin (PR) came from one randomised controlled trial comparing daclatasvir + PR with PR in patients with genotype 4. This found an SVR12 rate of 82 % in previously untreated patients. Serious adverse event rates associated with daclatasvir were low. The lack of comparative trial evidence for daclatasvir + sofosbuvir and many of the comparators defined in the NICE scope meant that established methods for comparing interventions either directly via head-to-head trial comparisons or via adjusted indirect comparisons were not feasible. Comparisons of SVR rates were therefore largely based on unadjusted estimates drawn from individual trial arms and subgroups of individual trial arms. The ERG concluded that, despite limited evidence, daclatasvir in combination with other treatments appeared to be associated with a high SVR rate. Daclatasvir + sofosbuvir was unlikely to be inferior to comparator treatments in genotype 1 patients; but, due to limited evidence, the relative efficacy of daclatasvir and other treatments in genotype 3 and 4 patients or patients with compensated cirrhosis was uncertain. The economic evaluation compared daclatasvir + sofosbuvir and daclatasvir + PR with a wide range of NICE-approved treatments for hepatitis C. The company submission focused on a series of subgroups defined by disease severity (METAVIR fibrosis stage F3, compensated cirrhosis), genotype and treatment history. In the cost-effectiveness analysis, daclatasvir-containing regimens were cost effective at a £20,000-£30,000 per QALY threshold in the following F3 populations: genotype 1 treatment naïve (Incremental cost-effectiveness ratio [ICER] = £19,739/QALY) and treatment experienced (£15,687/QALY) and genotypes 1, 3 and 4 interferon ineligible or intolerant (£5906-£9607/QALY depending on subgroup). In patients with cirrhosis, daclatasvir-containing regimens were not cost effective. The ERG found the company's economic analyses to be highly uncertain and in places biased. However, the ERG found that daclatasvir-containing regimens were cost effective in certain populations with significant fibrosis, and following new analyses by the company after a price reduction, in certain populations with cirrhosis, including patients who were not eligible for or who were intolerant to interferon therapy. The NICE Appraisal Committee's preliminary recommendation was that daclatasvir + sofosbuvir should be available as an option in genotype 1 and 4 patients with significant fibrosis but without cirrhosis, who had either been treated previously or were ineligible or intolerant to interferon. In response to the preliminary recommendation, the manufacturer submitted additional information including comparator SVR rates and a revised confidential price. Following this, the Committee expanded its original recommendation in its Final Appraisal Determination. The recommendation was expanded to include daclatasvir + sofosbuvir as an option for patients with significant fibrosis but without cirrhosis (in previously untreated patients with genotype 1, and genotype 3 patients ineligible or intolerant to interferon) and genotype 1, 3 and 4 cirrhotic patients who were ineligible or intolerant to interferon. Daclatasvir + PR was also recommended as an option for genotype 4 patients who had significant fibrosis or compensated cirrhosis.