Classification of depressive states is at the present time an open issue. Depression is ambiguously defined, either as a syndrom, or as a disease whose manifestation can be the depressive syndrom or other pathological manifestations (depressive equivalents). No agreement exists about the basic problem of the categorial or the dimensional nature of the classification, the later having being recently supported by several authors. The paper discusses the most commonly used classifications: the primary-secondary dichotomy, the ICD 9 and the DSM-III and especially the central problem of the endogenous-non endogenous dichotomy.