This paper contributes to the literature of the adoption of ERP systems and other existing and new IT-based innovation in developing countries. There is an imperative for a framework to explain the decision-making processes in ERP system adoption and vendor selection in general but particularly in developing Asian countrieswhereknowledgeonERPsystemsislimited. TheauthorsconductedinterviewswithITmanagersand end-users to identify factors affecting ERP system adoption and ERP system vendor selection by Thai-owned and multinational companies (MNCs) in Thailand. The findings from the study have led to the development of a research model of ERP system adoption. The paper presents a description and discussion of the model and identifies areas for its implementation and future research.