With an increase in intracranial pressure during epidural balloon inflation, epidural pulse waveform, which is polyphasic under normal conditions, becomes monotonous at about 30 mmHg. This change in waveform is considered closely related to the apparent increase in arterial driving pressure to the brain and to a disturbance of venous outflow. When cerebral vasodilatation is prominent, the waveform becomes monotonous at a significantly lower intracranial pressure. These findings correlate well with the results of spectral analysis of the pulse wave. The usefulness of change in epidural pulse waveform, which can indicate an alteration of intracranial pressure dynamics in a relatively low pressure range, is discussed with comparison to other techniques used to determine intracranial pressure dynamics.