this paper presents some of the conclusions of the research project ubacyt p601: "variations of the concept of madness in the work of j. lacan. its incidence in the differential diagnosis neurosis psychosis ", approved and funded for the period 2008-2010. it especially addresses the problematic issue of its conceptual delimitation in the lacan work, in which the term "madness" is used in several senses. this variety is reflected in its theoretical concept articulation and several clinical issues. the whole presentation of these work allows a wider vision of the benefits that brings to use any of the versions of "madness" concept that arise in the work of lacan. this work apply to the madness-psychosis articulation, addressing not only the conceptual issues, but also achieving a more precise definition of "madness"; and above of all it takes the big clinical problem in what we might call "mad psychosis".