Although B2B e-commerce represents today an important business activity with stable growth, it has not grown according to initial expectations, partly due to the difficulty in measuring its performance. Recent academic literature tries to explain the motivations and behavior of companies participating in electronic markets as well as the benefits deriving from this participation. Following this stream of research, the purpose of this paper is to present the preliminary results of a field survey studing e-marketplace participation across two dimensions: The first one examines the attitude of user companies towards e-marketplace participation (motivations, goals, expectations, fears etc.). The second dimension examines the perceptions of e-marketplace participants about the impact and benefits they derive from their participation as well as the factors affecting the perceived impact. The survey was conducted using a questionnaire, among participants of five e-marketplaces (a total of 62 companies participated), allowing for comparisons both between buyers and sellers and between different types of emarketplaces. The statistical analysis of the quantitative results renders interesting findings that come to confirm or compliment existing literature and indicate concrete directions for further research. The results indicate a generic transaction-based orientation of the e-marketplace participants towards the exchange, the negative effect of external pressure on benefits perception and the importance of participating years and company size to the impact of e-marketplaces.