Although pseudotumor cerebri is not the primary subject for the neurosurgical treatment, it is of clinical significance on differentiating from brain tumors and other similar lesions. The literatures concerning its clinical features and pathophysiology are reviewed with short summary of our eighteen cases. The incidence of pseudotumor cerebri, based on the clinical reports and our experience, seems to be low in Japan, which may be due to difference on races and/or diet. The visual acuity impairment is not always "benign" on its course, in contrast to other symptoms related to the increased intracranial pressure. CT scan is most useful for evaluating the ventricular size and abnormal densities. Contrast enhancement is required for detecting abnormal enhanced lesions. Angiography may disclose the dural sinus occlusion and/or dural arteriovenous malformation. Continuous measurement of intracranial pressure can show irregular change from high pressure to normal with or without episodic elevation in each case and on each day. It is reported that there is no rise of intracranial pressure in some cases. There are also some reported cases without papilledema. Various factors including increased blood volume, brain edema and impaired absorption of cerebrospinal fluid may play some role on the development of pseudotumor cerebri. The precise mechanism of small ventricle associated with impaired absorption of cerebrospinal fluid is still unclear. Further study about absorption and outflow resistance of cerebrospinal fluid, and alteration of blood volume and brain water content may resolve the pathophysiology of pseudotumor cerebri.