Fifty adult patients with severe brain injuries were examined with the EEG on the 1st, 2nd, 3rd, 5th, and 7th postoperative days. In 40 of these 50 cases a prognosis was given after 7 days as a result of the Fourier analysis of the EEG: 23 patients survived, 17 died. There are significant differences in the EEG's for these two groups: an increase of the absolute and relative amplitudes in the alpha and theta bands for the survivors, and a decrease or no change in the alpha and theta bands for the others, all during the first week. In 10 cases the correct prognosis could not be given: 5 patients showed spindle or alpha activity (alpha pattern coma) in the EEG; 4 cases had to be treated with barbiturates for focal seizures, and one suffered from secondary bleeding. In these cases computer tomography did not yield additional prognostic information.