AbstractDue to increasing demands in processing power on the one hand, but the physical limit on CPU clock speed on the other hand, multi-threaded programming is becoming more important in current applications. Unfortunately, multi-threaded programs are prone to programming mistakes that result in hard to find defects, mainly race-conditions and deadlocks. The need for tools that help finding these faults is immanent, but currently available tools are either difficult to use because of the need for annotations, unable to cope with more than a few 10 kLOC, or issue too many false warnings. This paper describes experiments with the freely available tool Helgrind and results obtained by using it for debugging a server application comprising 500 kLOC. We present improvements to the runtime analysis of C++ programs that result in a dramatic reduction of false warnings.