One hundred patients with decompensated hydrocephalus (60 operated, 40 nonoperated) were studied both retrospectively and prospectively at 3 moments of the disease course. The indicators were clinical: neurologic, psychic and social, and paraclinical: results of pneumoencephalography, encephalography, radioisotope cisternography. The effects of surgical treatment (ventriculocardiac derivation) and of medical treatment were evaluated at short and long term. In surgical treatment, favourable short-term outcome (headache, gait and micturition disorders, improved consciousness, psychomotor activity, social behaviour) was found in 88% of the patients; long-term favourable outcome was present in 60% of the patients and implied only the psychic and social indicators. In medical treatment the favourable short-term outcome was nonsignificant and the long-term outcome was favourable in only 32% of the patients. In the remaining cases evaluated as unfavourable, the cognitive disorders increased progressively. The predictors for favourable therapeutic outcome were: early diagnosis, early surgical intervention, the clinical form of hydrocephalus, the sequelae and short-term effects of surgical treatment.