BACKGROUND: This study was undertaken to determine the natural history of untreated skull base meningiomas. Although there are reports on the natural history of meningiomas, most series contain only a few cases of meningiomas involving the skull base. Natural history information is important when recommending treatment and evaluating results. METHODS: The case records and imaging studies of 40 patients with skull base meningiomas from a single practice were reviewed. These patients either did not receive treatment or there was a long delay from the onset of symptoms to the initiation of treatment. RESULTS: Skull base meningiomas may be very indolent tumors. Patients with these tumors have lived long, comfortable, and relatively productive lives without treatment or with delayed treatment. Impairment may be much less than imaging studies would suggest. CONCLUSION: The authors are not advocating that skull base meningiomas not receive treatment. However, their unique experience with this group of patients provides convincing evidence that the indolent behavior of some skull base meningiomas must be considered when recommending various surgical and radiation procedures and interpreting their results in relationship to the functional outcome of the patient.