Résumé
Many problems can be found in the start-up stage that may run the young firm to death. In this contribution, we try to understand what is really this crucial development period; especially we attempt to expose the characteristics in the management system of the young firm. A synchronism perspective and a diachronic one make it possible to expose four start-up scenarios. Each is defined and appreciated. This approach can make the future manager more responsible in front of several situations that have been described in the scenarios; he could also anticipate events and avoid some of them. Moreover it can allow future entrepreneurs think more intensively to their own project.