Concurrent object-oriented programs are hard to write because of the frequent use of state in objects. In a concurrent program, this state must be protected against race-conditions and deadlocks, which costs a lot of effort and is error-prone. Software transactional memory is a mechanism for concurrency control that is similar to mechanisms used in databases. The programmer does not deal with low-level locks, but instead uses transaction demarcation to protect shared memory.We show that in a statically typed subobject-oriented programming language, a transactional program requires less effort than writing a regular object-oriented programming. In addition, we show how transactionality can be added to existing classes without performing code transformations or using a meta-object protocol.