A general approach is discussed to assess the uncertainty surrounding the cost effectiveness ratio (C/E-ratio) estimated on the basis of data from a randomised clinical trial. The approach includes the calculation of a 95% probability ellipse and introduces the concept of a so called C/E-acceptability curve. This last curve defines for each predefined C/E-ratio the probability that the C/E-ratio found in the study is acceptable. The approach is illustrated by estimates of costs per life saved and costs per patient discharged alive on the basis of data from a phase II trial addressing the value of anakinra in treating sepsis syndrome.