Purpose: To conduct a systematic review (SR) of 550 studies produced between 1970 and 2008 that focus on programs and/or services provided by state vocational rehabilitation (VR) agencies believed to impact client and/or program outcomes. Method: Authors used a 5-step SR protocol to evaluate and summarize study content and outcomes, study design, and data collection methods. Results: Results indicate that the VR research base is highly varied in terms of the research focus with respect to programs and services, populations, and outcomes and that it spans across a wide range of research designs and data collection methods. Conclusions: The majority of the studies included in this review relied on administrative data, particularly Rehabilitation Services Administration data, and surveys. Only a small number of studies employed some type of experimental design, suggesting a lack of application of this type of research design. Implications and recommendations for future research are discussed.