Electroexpectogram (EXG) is a electropsychological curve obtained in a biofeedback based CNV paradigm. It is an evidence of the dynamics of the expectation process recorded during an extended, 100 trials CNV paradigm, where the onset and extinction of the CNV is controlled by the turning on and off the S2 stimulus of the paradigm.Since the introduction of the biofeedback design in the CNV paradigm (Bozinovska et al. 1988) we are recording various form of the EXG trace. We are now trying to make a taxonomy of the observed and recorded EXG traces.Several criteria can be used for that purpose. One criterion is the number of appearance of the CNV wave in the trace. Other criterion is the time interval between two extreme in the EXG trace. In such a way, during this phase of our work we are developing an initial taxonomy of the EXG traces, which we believe will be useful for clinical usage of the EXG trace.