Enterprise Application Integration (EAI) is a concept that becomes more interesting in many organizations. Various computer systems shall share their functionalities with other systems to achieve support for new requirements. One approach for integration is the exchange of messages between participating applications. Like in other domains of IT, also for integration with messaging patterns were found and collected. Patterns describe a common solution for recurring problems. In the open source domain some frameworks have been developed that settle in the EAI domain. This thesis shall find out which patterns are supported and can be implemented with the help of open source frameworks. The frameworks used are Apache ActiveMQ, Apache Camel, Apache ServiceMix and Codehaus Mule. To achieve this, the four frameworks will be taken under investigation. The support for patterns shall be found out by studying documentation on the one side and implementing scenarios on the other side. By doing this it shall also be found out how easy it is for developers to use and which problems can arise when using a certain framework. Furthermore parts of EAI solutions will be observed to analyze which of them are covered by the used frameworks. At last a short examination of business aspects will be accomplished to find out if it is beneficial for an enterprise to use open source frameworks for application integration.