A total of 55 polygraphic recording (ICP, EEG, EMG, EOG, Respiration, and ECG) were made in 20 comatose patients following cranial injuries, during the week after the injury. Whenever the ICP was stable, and without waves, and whatever the mean values were, the EEG tracing was slow, monomorphic, of large amplitude, and nonreactive. Each time that ICP recordings included Lundberg's B waves, the EEG tracings showed alternating bursts of slow waves and periods of rapid activity, with or without typical sleep patterns. The ICP increases each time there is flattening of the tracing and diminishes with the reappearance (spontaneous or provoked) of slow waves. The artificial respiration is not always involved in determining these phenomena.