The present thesis contributes to the user acceptance literature by improving understanding about the role of pre-implementation acceptance in the adoption of enterprise systems. This phenomenon was addressed from three different perspectives in the three core papers: Chapter 2 focused on strategies to foster acceptance of enterprise systems, while informing theory about the antecedents of perceived usefulness and perceived ease of use; Chapter 3 developed the pre-implementation acceptance model to measure and explain the relationships between the factors that determine acceptance of enterprise systems; and Chapter 4 empirically tested the relationship between job-related indicators that represent the organizational context in which the enterprise system will be implemented and the acceptance of the technology. The present thesis advances understanding about the relationships between the different factors that influence acceptance, creates awareness about the importance of the pre-implementation phase in determining the success or failure of implementation, and provides advice for organizations on how to foster acceptance. This thesis offers a new theoretical framework based on the user acceptance and social psychology literature, allowing a more accurate measurement of the acceptance of enterprise systems during the pre-implementation phase.