Electroencephalographic (EEG) techniques provide an interface between behavioral studies and more mechanistically directed neurophysiological studies, thus constituting a potentially important in vivo method of neurobehavioral assessment. The amplitude and frequency of the EEG signal depends on the behavioral state of the subject and the location of the recording electrode. Systematic assessment of EEG recordings may reveal alterations in integrated neuronal function induced by drug or neurotoxicant exposure. Fourier analysis allows more precise analysis of the frequency content of the recorded signal and yields data that may be further reduced and statistically analyzed. EEG data from neuropharmacologic and neurotoxicologic studies are discussed to illustrate application of power spectral analysis techniques in experimental laboratory settings.