The cost-effectiveness of prescribing HA-1A for sepsis patients was analyzed by comparing effectiveness and direct medical costs. Effectiveness was estimated on the basis of published data from a randomized clinical trial. Costs were determined by combining data from the same trial with expectations about hospital days. Average costs per life year gained were estimated at 25,000 Dutch guilders (1 Dutch guilder is approximately 53 US cents). Sensitivity analyses were applied and showed that the effectiveness and cost-effectiveness of treating patients with HA-1A depend a great deal on the expected duration of survival after successful treatment. If the objective is to maximize the cost-effectiveness of treatment, this means that the prognosis of the patient should be considered when deciding about the appropriateness of treatment with HA-1A. As one would expect, another way to increase cost-effectiveness would be to increase the proportion of gram-negative sepsis patients amongst those receiving treatment.