Experience with a continuous-pressure controlled, external ventricular drainage system (EVD) in 100 patients (n = 49 female, n = 51 male; mean age, 56.3 yr) with acute hydrocephalus is reported. Cerebrospinal fluid circulation disturbances resulted from hemorrhages caused by subarachnoid hemorrhage (n = 45), parenchymal hemorrhages from angioma (n = 4), anticoagulants (n = 7), or hypertension or other reasons (n = 30); in addition, hydrocephalus developed from infections (n = 3), tumors (n = 2), infratentorial infarction (n = 5), or unknown reasons (n = 4); 52 patients had ventricular hemorrhages. No patient died of system-associated morbidity. Mean time of EVD treatment was 9.5 days, with 40 patients being treated for 10 to 29 days; routine refobacin (5 mg) flushing of the system was performed three times a day. Patients without cerebrospinal fluid leakage had a 2% rate of secondary infection compared with 13% in patients with cerebrospinal fluid leakage due to ventricular catheter placement (P < 0.05; overall infection rate, 5%). A clinical mortality rate of 29% during EVD treatment was observed in subarachnoid hemorrhage patients (Hunt and Hess Grades II, III, IV, and V; n = 9, 9, 18, and 9, respectively); recurrent hemorrhages during EVD treatment occurred in 19 patients (26 hemorrhages), and of these, 10 patients died. System occlusion was seen in 19 cases (12 of 45 patients with subarachnoid hemorrhage), requiring catheter and system renewal in 1 case; system extraction was seen in 3 cases, misplacement was seen in 11 cases, and disconnection was seen in 5 cases.(ABSTRACT TRUNCATED AT 250 WORDS)