Transactional Memory (TM) has received a lot of attention as a programming API for concurrent programs on emerging multicore architectures. If the transactional programming model is to realize its promise of simplifying the problem of writing correct and scalable concurrent programs, debuggers will have to change. In this paper, we introduce tm db, an open-source library to provide debuggers with a general debugging support for transactional programs. The library helps debuggers provide programmers with generic transactional debugging features, independent of the particular TM’s runtime internals. In addition, it provides TM designers with a well defined interface for transactional debugging support. We discuss the basic debugging features we believe are essential to debug transactional programs, how they are provided by the library, and how they integrate into a general debugging infrastructure.