Background: Information to judge both the internal and external validity of health behavior research conducted in healthcare settings is vital to translate research findings to practice. This paper reviews the extent to which this research has reported on elements of internal and external validity, with emphasis on the extent to which research has been conducted in representative settings with representative populations. Methods: A comprehensive review was conducted of controlled interventions for dietary change, physical activity, or smoking cessation conducted in healthcare settings and published in 12 leading health behavior journals between 1996 and 2000. Using the RE-AIM (reach, effectiveness, adoption, implementation, maintenance) framework, the characteristics and results of these studies were summarized to document the extent to which intervention reach, adoption, implementation, and maintenance were reported and what has been learned about each of these dimensions. Results: A total of 36 studies qualified for review. Participation rates among eligible patients were reported in 69% of studies and were generally quite high; in contrast, only 30% of studies reported on participation rates among either healthcare settings or providers. Implementation data were reported in 77% of the studies and these rates were generally high, with the caveat that intervention was often delivered by paid research staff. Long-term maintenance results were reported very consistently at the individual level, but program continuation was almost never reported at the setting level. Conclusions: We conclude that a much stronger emphasis needs to be placed on the representativeness of providers and settings that are studied. Examples of how this can be done and recommendations for future research are provided.