Establishing and managing reputation has become a critical issue for Cloud Computing. In this paper we investigate this issue and propose our conception for the management of Reputation in Cloud Computing. This conception is based on the extensive use of SLA through the whole life cycle of the reputation. With this objective in mind we focus on defining and describing the close relations that exist between the establishment of reputation and the management of SLA. In this perspective we identify key aspects and mechanisms to develop a truly efficient Reputation management based on the use of SLAs.