Despite the benefits that can be achieved from a successful ERP system implement ation, there is already evidence of high failure risks in ERP implementation pro jects. Too often, project managers focus mainly on the technical and financial a spects of the implementation project, while neglecting or putting less effort on the nontechnical issues. Therefore, one of the major research issues in ERP sys tems today is the study of ERP implementation success. Some authors have shown t hat ERP implementation success definition and measurement depends on the points of view of the involved stakeholders. A typical approach used to define and meas ure ERP implementation success has the been critical success factors approach. Along this line, in this research we seek to contribute to our understanding of the critical success factors of ERP implementations and how these critical succe ss factors can be put into practice to help the process of project management in ERP implementations. We attempt to build a consensus from previous research and to derive a unified model of critical success factors in ERP implementations. For this purpose we apply grounded theory as our main research method. We have c ollected all the relevant research material and we have coded it. To increase th e validity and reliability of the study, the several information sources have be en triangulated and inconsistencies have been clarified with additional document ation. This study provides the results of the open coding process from our appli cation of the grounded theory method. After the coding step, we obtain an initia l unified model of the critical success factors in ERP implementations. We then map these critical success factors in a matrix with four perspectives: organisat ional, technological, strategic and tactical.