The status of the ATLAS simulation project for the LHC startup

The commissioning phase for the ATLAS experiment, being now so imminent the LHC startup, is a challenge for every development performed up to now. Along this line, the simulation program is nowadays operational and running with full functionality within the ATLAS common framework Athena. The latest developments concern an enhanced versatility, to cope with the increasing needs of developers and users, an easiness in use by a big community such as ATLAS reaching now more than 2000 potential users. Emphasis in this talk is towards the new functionality recently added, validation and production strategy as well as improved robustness and maintainability.