Three separate topics are covered in this review. The first deals with the technique of signal averaging. The concept of ensemble averaging is explored, and alternatives to this traditional tool are considered such as crosscorrelation averaging, latency corrected averaging, median averaging, etc. Different measures of variability of single evoked potentials are finally discussed. The second topic deals with modeling of the evoked potentials. The direct and inverse problems of source localization are discussed. Recent results of the application of these techniques to single evoked potentials are given. The third topic deals with the use of principal components for signal representation and comparison. Geometric consideration and varimax rotation of coefficients are discussed and examples given.