When we want to quantify an experimentation on an individual presenting behaviour troubles, the problem we are faced with is the relative inadequacy between the techniques that are used and the patient. The aim of this research is a study of the evolution of the differential analysis of power spectra and alteration in the repartition of VEP amplitudes on 18 depressed adults before and after antidepressive treatment. Control in healthy adult volunteers has been realised. The originality of the method used is in the analytical techniques and selected tests. It is difficult to state positively that VEP morphology represents a pertinent criterion in the study of the evolution of a depressed syndrome. But the results which are obtained show a similar evolution between VEP morphology and clinical criterion. This is in conformity with numerous present studies which consider VEP as a pertinent sign in a psychophysiological process.