Olfactory meningiomas are benign, slow-growing intracranial tumors arising from the dura along the cribriform plate. The first clinical symptom is anosmia followed, usually after several years, by dementia and visual deterioration. A series of 36 patients are presented; in all cases but one, their conditions were diagnosed late and not until the tumor had reached a very large size. By the time the proper diagnosis was made and the tumors were surgically removed, mental or visual disability was often irreversible. Conditions of patients initially seen with anosmia should be investigated by presently available noninvasive diagnostic methods including computed tomographic scanning.