20 psychiatric patients without pharmacologic therapy and an homogeneous control group of 19 healthy subjects have been submitted to an electroencephalographic (EEG) investigation. Computerized spectral analyses of the main EEG frequency bands have been performed. The spectra have been determined by some geometrical descriptors: the relative activity, the barycentric frequency and the barycentric radius; also classic descriptors have been used as complementary ones. In the EEG profìle signifícant differences between patients and healthy subjects have been found. Some differences have also been observed among subgroups of schizophrenic patients. The geometrical descriptors applied in the EEG analysis are suggested as a useful method in the description of the basic characteristics of the main EEG frequency band