It is generally agreed that patients have a right to be adequately informed. However, little is known about the extent to which doctors and patients agree about information that should be disclosed. We studied what patients want to know, as contrasted with what physicians report actually disclosing, in a population of physicians who treat seizures and patients or parents of patients who have this disorder. In general, it was found that patients prefer far more detailed disclosures than physicians routinely offer and that the two groups have widely different beliefs about the consequences of detailed disclosures. Patients and parents preferred extensive disclosures, particularly regarding risks and alternative therapy. Physicians were likely to disclose only risks with a relatively high probability of occurrence and they provided little information about alternative therapies. Patients and parents were also much more likely than physicians to believe that the final decision concerning therapy should rest with the patient. The data suggest that a better empirical understanding of the consequences of detailed disclosures may help resolve differences of opinion regarding how much information should be provided to patients.