Brain mapping of EEG and evoked potentials permits the topographic display of electrical activity of the brain and is superior to conventional polygraphic procedures. Data from 16 scalp electrodes and two ear reference electrodes were worked up. The spontaneous EEG and the EEG during different testing conditions to activate particular brain regions was measured. 2s EEG data segments were subjected to spectral analysis by a fast Fourier transformation (FFT). For late evoked potentials (VEP, AEP, SEP and P300) a single value representing the amplitude of EP at each 2-ms poststimulus latency point served for subsequent topographic mapping. Statistical technique (Student''s t-test) have been used in conjunction with EEG and EP data to render visible the regions where a clinical population differ from normal subjects. The results show abnormalities of EEG and EP in patients with psychical and neurological diseases.