Three neonates with herpes encephalitis had serial cranial ultrasound and CT studies performed during their hospitalization. Initially, subtle changes of diffuse brain edema were present but with no ventricular compression. A second phase revealed progressive brain edema with ventricular compression. A third phase with enlarging ventricles indicates developing encephalomalacia. Occasionally cyst formation may be noted within the cerebral white matter, a phenomenon initially more readily evident by ultrasound.