This paper has reviewed progress in isotopic and environmental tracer methods applied to a wide variety of settings. A few are truly ``new'' developments; most are refinements of previously suggested methods. Many suggest the potential for contributing significantly to our understanding of subsurface hydrological systems. However, the most encouraging development is the publication of a large number of studies in which isotopic and environmental tracers are only one among a variety of investigative techniques employed. Unless considered in the context of a thorough evaluation of the physical hydrogeology, tracer results are of generally of limited value. Conversely, isotopic and environmental tracers can usually provide very useful constraints on interpretations of subsurface flow regimes. Although the papers reviewed show significant progress toward the goal of integrating tracer methods into routine subsurface hydrology, they also show that there is far to go before the goal is fully realized.