The shift from a product-based to a knowledge-based economy is resulting in an increased demand for knowledge workers who are capable of higher-order thinking and reasoning to solve intricate problems in the work place. This requires organizations to implement knowledge management systems (KMS) at an accelerating pace to facilitate the work of their employees. However, the large investment requires for a KMS has made it imperative for organizations to understand the factors that contribute to employees' acceptance of KMS. This paper draws attention to users' concerns about loss of power and influence through the sharing of information/knowledge via KMS. We propose a new construct, perceived power security, to examine the applicability of the Technology Acceptance Model (TAM) in explaining the decisions of the employees to accept KMS. The results based on a sample of 145 employees taken mostly from four international semiconductor manufacturing companies in the Hsin-Chu Science-based Industrial Park in Taiwan strongly support the extended TAM in predicting employees? behavioral intention to use KMS.