Methodologies based on symbolic dynamics havesuccessfully demonstrated to reflect the nonlinear behavior of biological signals. In the present study, symbolic dynamics wasapplied to the electroencephalogram (EEG) in order to describe the level of depth of anesthesia. The EEG was transformed tosymbol sequences. Words of three symbols were built from this symbolic series. The results obtained from the EEGs of 36patients undergoing anesthesia showed that the probabilities of the word types were able to reflect the depth of anesthesia in asimilar way to the auditory evoked potential index AAI, a commercial index.