Cost-effectiveness analyses routinely ignore the value of diagnostic certainty. Moreover, no previous study has compared this value among different stakeholders. We surveyed 25 patients, 28 physicians, and 23 managed care executives to compare their willingness to pay for diagnostic information for peptic ulcer disease. Patients (84%) were most likely, and executives (43%) least likely, to be willing to pay at least $1 (median willingness to pay < $50). Differences in willingness to pay among stakeholders indicate potential for conflicts over access to tests. Although nearly all patients valued diagnostic certainty, its value was generally small and insufficient to change the cost-effectiveness ranking of treatment alternatives.