Clinical decision analysis is a technique which is used to deal with uncertainities in clinical medicine. We used this technique to compare the cost-effectiveness of chloramphenicol and ciprofloxacin in the treatment of enteric fever. The study shows that the most economical alternative can be predicted if the cost of hospital stay and the sensitivity of the organism to chloramphenicol are known. Thus if the hospital costs are Rs 50/- per day, chloramphenicol will be the drug of choice if more than 52% of the organisms are sensitive to the drug. At lower levels of sensitivity to chloramphenicol, ciprofloxacin will be the drug of choice.