Idiopathic normal pressure hydrocephalus (iNPH) is a syndrome characterized by gait disturbance, dementia, and/or urinary incontinence without causative disorders, and ventricular enlargement due to disturbance of the cerebrospinal fluid (CSF) circulation. The number of patients with iNPH will increase with the aging of the population in Japan. However, iNPH is often difficult to differentiate from other senile disorders such as lumbar canal stenosis, parkinsonism, and so on. Clinical guidelines for iNPH are required to improve understanding and provide for patients’ quality of life and social care. These guidelines propose three levels of iNPH: possible, probable, and definite. Possible iNPH includes one or more of the classical triad and ventricular dilation in middle aged and elderly patients with closing of the CSF space at high convexity on magnetic resonance imaging. Probable iNPH shows improvement of the symptoms after CSF removal in patients with possible iNPH. Definite iNPH shows clinical improvement after CSF shunt operation. The CSF tap test is a major diagnostic measure because of the simplicity and less invasiveness. Use of the programmable valve is recommended to decrease CSF overdrainage. These guidelines are helpful for the diagnosis and treatment of iNPH.