An approach for brain electrical activity mapping using a personal computer has been investigated to enhance the visibility of the EECs. An automatic procedure from data acquisition to the final mapping has been developed for on-line or off-line data processing, in which a table-look-up technique has been introduced to eliminate redundant processing. The power spectra in different EEC frequency bands for four electrodes are coded into 15 colors and mapped on a color monitor. The data correspondings to the areas between electrodes are interpolated by the surface spline method. The mapping speed and smoothness has been optimized. An experiment has been clone for 6 subjects, including a normal person, and five patients with different medical histories. The results are mostly in agreement with the pathological reports and can detect sonic underlying brain dysfunctions which EEC specialists may fail to see. This method may offer an important tool for clinical diagnosis and for future brain study.