Abstract The objective of the offline framework is to reconstruct and analyse the data coming from real interactions. The ALICE Offline framework, AliRoot, has already been used during the production of the Technical Design Reports of each detector to optimise their design and it is currently used to evaluate the physics performance of the full ALICE detector. This paper describes the AliRoot software environment. We wish to put into perspective the main decisions and the organisation of the offline project. First a general description of the ALICE offline framework (AliRoot) is given, starting with a short historical background followed by a description of the simulation, reconstruction and analysis architecture and the organisation of the ALICE offline project. Finally we briefly indicate the main conclusions of our work on AliRoot.