The authors have studied 142 cases of pericerebral fluid collection, by ultrasound. Three echographic patterns are individualized: anechogenic single compartment (109); thin linear echogenic membrane dividing the pericerebral fluid collection (25); the third group (8) presented with a peripheric echogenic collection. The use of high frequency probes permits the detection of pericerebral effusions, and provides new information about the high incidence. Ultrasound can define the anatomical position and show the complications which are mainly acute subdural hematoma.