In the 1990s, Enterprise Resource Planning (ERP) systems were the pioneers in business process management, by replacing legacy systems which became obsolete. These first implementations faced countless problems, but mainly, the lack of experience of all the parties involved. Quite a few of these experiences and difficulties have been documented over the years; But, all this literature being very different from each other, makes it difficult to unify criteria. However, some have proposed an integrative methodology from the study of the published literature. This research develops the descriptive-comparative analysis between the integration approach and the methodologies used in practice, such as the ones used by consulting firms like: Ernst & Young and Deloitte; ERP development firms: SAP and Oracle, as well as OpenERP and OpenBravo, from the open software community. The results point to Deloitte's proposal as the most complete, although the majority of these methodologies neglect the tactical aspect of such implementations. Key Words: ERP, Implementation, Methodologies, Open Source Software, Integrative Approach, Development Firms ERP Methodologies, Consulting Firms Erp Methodologies.