To assess the clinical and cost-effectiveness of drotrecogin alfa (activated) for the treatment of adults with severe sepsis in a UK context. Electronic databases. Data from the commercial use of the drug up to April 2002. Data from the manufacturer submission to the National Institute for Clinical Excellence (NICE). A systematic review of the literature and an economic evaluation were undertaken. Data were synthesised through a narrative review with full tabulation of results from included studies. The evidence on the effectiveness of drotrecogin alfa (activated) for the treatment of severe sepsis came primarily from one large pivotal randomised controlled trial, the PROWESS study. This study demonstrated a statistically significant absolute reduction in 28-day mortality of 6.5%. Longer term survival benefit was maintained to 90 days. By 9 months, the trend towards increased median survival was non-significant, although the survival curves did not cross. Results presented by the number of organ dysfunctions were not statistically significant, but when mortality rates for those with two or more organ failures were combined, the relative risk of death was significantly lower in those treated with drotrecogin alfa (activated) compared with placebo. However, this report highlights a number of considerations relevant to the subgroup analyses reported for the PROWESS study. Published cost-effectiveness studies of treatment with drotrecogin alfa (activated) have applied a range of methods to the estimation of benefits, estimating an incremental gain per treated patient of between 0.38 and 0.68 life-years (for patients with severe sepsis). For patients with severe sepsis and multiple organ dysfunction, the manufacturer (Eli Lilly) estimated an incremental gain of 1.115 life-years per treated patient, compared to 1.351 life-years per treated patient estimated by the Southampton Health Technology Assessments Centre (SHTAC). These latter UK analyses are based on a patient group that is more severely affected by disease, where effectiveness is greater and the baseline risk of all-cause mortality is much higher (SHTAC analysis), these factors are associated with the noted difference in effect. The three published cost-effectiveness studies report cost for US and Canadian patient groups; for those patients with severe sepsis they report the additional cost per patient treated in a range around 10,000-16,000 dollars. The manufacturer's submission reports analysis for the UK, based on 28-day survival data in patients with severe sepsis and multiple organ dysfunction (the European licence indication), with the additional mean cost per treated patient estimated to be 5106 pounds. The analysis undertaken by SHTAC, for a UK group of patients with severe sepsis and multiple organ dysfunction, estimates an additional mean cost per patient treated of 6661 pounds. The manufacturer's submission to NICE presents cost-effectiveness estimates for drotrecogin alfa (activated) in the UK, in patients with severe sepsis and multiple organ dysfunction, at 6637 pounds per quality-adjusted life-year (QALY) based on 28-day effectiveness data, and 10,937 pounds per QALY based on longer term follow-up data. SHTAC developed an independent cost-effectiveness model and estimated a base-case cost per QALY of 8228 pounds in patients with severe sepsis and multiple organ failure (based on 28-day survival data). Simulation results indicate that where the NHS is willing to pay 20,000 pounds per QALY, drotrecogin alfa (activated) is a cost-effective use of resources in 98.7% of cases. Published economic evaluations report various sensitivity analyses, with results sensitive to changes in the measure of treatment effect, but otherwise studies reported that results were robust to variations in most assumptions used in the cost-effectiveness analysis. Drotrecogin alfa (activated) plus best supportive care appears clinically and cost-effective compared with best supportive care alone, in a UK cohort of severe sepsis patients, and in the subgroup of more severely affected patients with severe sepsis and multiple organ failure. The introduction of drotrecogin alfa (activated) will involve a substantial additional cost to the NHS. The treatment-eligible population in England and Wales may comprise up to 16,570 patients, with an estimated annual drug acquisition cost of over 80 million pounds, excluding VAT. Further research is required on the longer term impact of drotrecogin alfa (activated) on both mortality and morbidity in UK patients with severe sepsis, on the clinical and cost-effectiveness of drotrecogin alfa (activated) in children (under 18 years) with severe sepsis, and on the effect of the timing of dosage and duration of treatment on outcomes in severe sepsis.