Technology upgrades are an inevitable part of dealing with any man-made invention utilized for productive gain. One key technology used for productive gain within a firm is enterprise software, specifically a firm's Enterprise Resource Planning (ERP) system. After the adoption of an ERP system, an organization is perpetually faced with the significant decision of when to migrate to a newer version of that ERP system. Even with this inevitable need to replace existing technology, firms could still choose to reject the new technology and not upgrade to a newer version of enterprise software. The purpose of this study is to gain a better understanding of the differences in the propensity of firms to initiate and commit to the assimilation of a technology upgrade, specifically to the firm's ERP system. By synthesizing and integrating theory and literature from Diffusion of Innovation (DOI), Product Life Cycles (PLC), and Relationship Marketing (RM), this study aims to understand how contextual effects influence the assimilation of an ERP version upgrade by a firm. Using the Technology-Organization-Environment (TOE) theoretical framework, three different contextual factors are evaluated in this research: technological, organizational, and environmental. A research model is proposed that advances hypotheses specific to this enterprise software domain. A quantitative assessment of the research model is tested using a sample of customers of a single ERP vendor: SAP. Based upon an examination of the context of the firms and the classification of the firms into assimilation stages, differences emerged that explained the propensity of a firm to assimilate a new ERP version. Those firms with a higher propensity to assimilate the new version had a higher assessment of relative advantage, IS technical competence, and the strategic role of IS relative to those firms with a lower propensity to assimilate a new ERP version. At the same time, those firms with a lower propensity to assimilate a new ERP version had a higher sense of trust with the ERP software vendor. The findings of this dissertation confirm that internal and external forces influence a firm's assimilation of an enterprise software upgrade. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]