The flexibility offered by an Enterprise Service Bus (ESB) in enabling various applications to exchange data makes it a very important middleware layer that is responsible for transporting data in a Service-Oriented Architecture (SOA). The popularity of the ESB has given rise to a number of commercial off the shelf (COTS) products as well as open source ESBs. In this study, we evaluated three open source ESBs and compared them both qualitatively and quantitatively. The empirical results were statistically tested to determine the statistical significance of the results.