TheGAUDIsoftwareframeworkistobeusedforallevent-processingapplicationsintheLHCbexperiment.TheGEANT4toolkithasbeenintegratedintoGAUDItoformthebasisoftheLHCbsimulationprogramGAUSS.Thebenefitsofthisapproacharethatitpermitsre-useofbasicservices,suchaspersistency,interactivityanddatavisualization,aswellasphysicsalgorithmsthatwereoriginallydevelopedinthecontextofthereconstructionandanalysisprograms.FollowingtheGAUDIphilosophy,theintegrationhasbeenachievedbydevelopinganumberofserviceswithabstractinterfacesthatcanbepluggedinatrun-time.Wedescribetheoveralldesignanddetailsofthecomponentsforinterfacingthedetectorgeometry,theprimaryinteractionandtheoutputfromtrackingparticlesthroughthedetector.