The purpose of this study, commissioned by the Ministry of Justice, was to report on the state of positive law on guarantees and other personal guarantees. The guarantee, which was presented less than 30 years ago as a security in decline, seems to have seen considerable renewal in practice since then. In any event, it gives rise to ongoing litigation at the same time as it has given rise, for some 15 years, to extraordinary legislative and, above all, case-law. As a result, a sector of law which has remained stable since the Civil Code has been disrupted. In return, however, there is a lack of confidence in the guarantee on the part of certain creditors who turn to new forms of personal security not governed by law. Thus, in order to better understand the ‘crisis’ of the spontaneous guarantee diagnosed, it appears necessary to supplement the analysis of the legislative and case-law rules relating to that contract and other personal guarantees with a (necessarily limited) approach to the litigation brought about by those guarantees. Although the proceedings before the courts dealing with the substance of the case appear only on the basis of the figures of the claims brought before them, it was possible, on the other hand, to conduct a systematic study of the disputes relating to guarantees and other personal guarantees before the Cour de cassation. On the basis of the CD Rom Lexilaser Cassation 1986-1995, all the judgments handed down by the Cour de cassation (Court of Cassation) over the last ten years have been recorded. The census provided a clear idea of the types of guarantee that give rise to litigation, the types of questions raised, and the concrete results obtained by those involved. This information is not only valuable in itself: they also shed new light on the rules of case-law which emerge from the judgments delivered, for example by making it possible to ascertain to what extent a rule, favourable in its wording to a particular actor, actually enables it to obtain a positive concrete result before the Cour de cassation. The report examines in turn the guarantee and then the other personal security. The first part begins with an analysis of the dispute arising from the guarantee, followed by a detailed study of the legislative and case-law solutions on the various issues (validity of the guarantor’s undertaking, extent of that undertaking, termination of the guarantee, a place reserved for specific problems connected with the opening of collective proceedings against the debtor). The second part, which is much shorter, offers the main guarantees of substitution for the guarantee (letters of intent, first-call guarantees, delegation, solidarity), as they appear in the judgments of the Cour de cassation. The conclusion opens some avenues for discussion with a view to a possible legislative reform in the area of personal security.