Knowledge map systems gather explicit and acquired knowledge which can be shared, and facilitate the emergence of tacit knowledge of new relationships. A variety of people use knowledge map systems to engage in knowledge sharing. However, while most studies focus on system design for knowledge map systems, predictors for a knowledge map system adoption have seldom been addressed. This paper proposes a model to facilitate knowledge sharing in communities of practice for a knowledge map system. Both theoretical and empirical analyses were undertaken and are reported here to explain the factors that influence users' adoption of knowledge map systems to share knowledge using the technology acceptance model (TAM) which incorporates system characteristics and knowledge map system self-efficacy. The proposed model was empirically evaluated using survey data collected from 179 virtual community users about their perceptions of knowledge map systems. Overall, the data used fit well with the hypothesized relationships in the model, as all relationships in it were statistically significant. The findings suggested that both system characteristics and users' knowledge map system self-efficacy positively affected user perceptions and behavioral intention. The results also revealed a positive relationship between attitude and intention in the adoption of knowledge map systems. Implications of these results are discussed.