The authors investigate the extension of dynamic data race detection techniques developed for sequentially consistent systems to weak systems. A potential problem is that in the presence of a data race, weak systems fail to guarantee sequential consistency and therefore dynamic techniques may not give meaningful results. However, the authors reason that in practice a weak system will preserve sequential consistency at least until the 'first' data races since it cannot predict if a data race will occur. They formalize this condition and show that it allows data races to be dynamically detected. Further, since this condition is already obeyed by all proposed implementations of weak systems, the full performance of weak systems can be exploited.