Due to the importance of knowledge in today's competitive world, an understanding of how to enhance employee knowledge sharing has become critical. This study develops an integrated model to understand key factors of employee knowledge sharing intentions through constructs prescribed by two established knowledge management research streams, namely, those concerning individual motivations and social capital. This study classifies employee knowledge sharing intentions as either tacit or explicit and investigates whether the level of the determinants and their influences differ between the two. The research model is tested with survey data collected from 2010 employees in multiple industries. Analysis results show that the proposed model significantly explains the variance of employees' tacit and explicit knowledge sharing intentions. This finding indicates that the model's unified perspective enhances our knowledge of how to improve employee knowledge sharing. The new findings reveal that organizational rewards have a negative effect on employees' tacit knowledge sharing intentions but a positive influence on their explicit knowledge sharing intentions. The analysis results confirm that reciprocity, enjoyment, and social capital contribute significantly to enhancing employees' tacit and explicit knowledge sharing intentions. Additionally, these factors have more positive effects on tacit than on explicit knowledge intentions. The implications of the new findings are discussed. (C) 2012 Elsevier Ltd. All rights reserved.