This paper presents a summary of the evidence review group (ERG) report on the clinical effectiveness and cost-effectiveness of rituximab with chemotherapy compared to chemotherapy only for the treatment of relapsed/refractory chronic lymphocytic leukaemia (CLL) based on the manufacturer's submission to the National Institute for Health and Clinical Excellence (NICE) as part of the single technology appraisal (STA) process. Evidence was available in the form of one open-label, ongoing, unpublished randomised controlled trial (RCT), REACH (Rituximab in the Study of Relapsed Chronic Lymphocytic Leukemia), conducted by the manufacturer, which compared rituximab with a fludarabine and cyclophosphamide combination (R-FC) to fludarabine and cyclophosphamide (FC) only. REACH was scheduled to run for 8 years; however, the data provided were immature, with a median observation time at the time of data analysis of 2.1 years. REACH provided evidence of prolonged progression free survival with R-FC compared to FC (10 months, investigators' data), but no evidence of an overall survival benefit with R-FC. Patients refractory to fludarabine and with prior rituximab exposure were excluded from REACH and no controlled studies were identified by the ERG for these patient groups. The ERG had concerns about the structure of the economic model submitted by the manufacturer, which did not allow improvement in quality of life from treatment while in a progressed state. The manufacturer's model further assumed a divergence in cumulative deaths between the R-FC and FC treatment arms from the outset, which did not accord with observed data from REACH. When the survival advantage was removed, the manufacturer's base-case incremental cost-effectiveness ratio (ICER) changed from 15,593 pounds to between 40,000 pounds and 42,000 pounds per quality-adjusted life-year (QALY). With no survival advantage, the ICER became sensitive to changes in utility. There was no good empirical evidence on the utility of CLL patients in different states. Allowing for the possibility of a survival advantage with rituximab (although not supported by current evidence), the ERG performed further modelling, which found that rituximab would be cost-effective at 20,000 pounds/QALY (30,000 pounds/QALY) if a reduction in survival advantage relative to the manufacturer's base case of 40% (80%) was assumed. The guidance issued by NICE in July 2010 as a result of the STA recommends rituximab with FC for people with relapsed or refractory chronic lymphocytic leukaemia, except when the condition is refractory to fludarabine or where there has been previous treatment with rituximab.