The purpose of this paper is to present in a uni¯ed context the reduced form modelling approach, in which a credit event is modelled as a totally inaccessible stopping time. Once the general framework is introduced (frequently referred to as \pure intensity" set-up), we focus on the special case where the full information at the disposal of the traders may be split in two sub-¯ltrations, one of them carrying the full information of the occurrence of the credit event (in general referred to as \hazard process" approach). The general pricing rule when only one ¯ltration is considered reveals to be non tractable in most of cases, whereas.
