Workable criteria are proposed that allow early recognition of mild forms of occult hydrocephalus and correlated disorders. Two groups of patients are analyzed, i.e., a group of twelve mild but classical forms of low-pressure hydrocephalus and another group of 20 patients with atypical clinical forms of disorders of the CSF dynamics. Two control groups are presented for neuropsychological comparison purposes: a normal control group of 50 subjects and a small group of three commissurotomized subjects. Patients with an overt demential syndrome due to a normotensive hydrocephalus syndrome were excluded from the study. The authors found the grasp reflex of the foot and the tonic foot response to be present in all cases with the Hakim and Adams triad. In such cases the grasp reflex is usually accompanied by the forward groping of the foot and the grasp reflex of the hand. The most helpful and useful clinical findings for an early diagnosis are the presence of the grasp reflex of the foot and of the tonic foot response of the sole in such organic brain-damaged patients with (1) a normal routine neurological examination and (2) an apparently normal mental status and even with a rather normal IQ. These reflexes are usually the single objective clinical findings in all forms of mild and occult disorders of the CSF dynamics, i.e., low-pressure hydrocephalus syndromes, cerebral atrophies and mixed forms cases. The next step for the diagnosis consists in a conventional IQ evaluation and a battery of tests exploring more specifically the sensorimotor integration, i.e. bimanual vs. unimanual activity, the Kohs block design test and part of the Halstead-Reitan neuropsychological test battery.