Summary: The Java Platform, Enterprise Edition (Java EE, previous term: J2EE) has been designed to permit the use of Java for mission critical transactional business applications such as financial accounting or enterprise resource planning systems. When programming such applications it is still difficult to assure the isolation between transactions executing in parallel. Compliance with transaction isolation is a basic requirement to keep underlying data in a consistent state. This paper analyses existing problems and gives an overview of the solutions that are presently available or under discussion.