Researchers have evaluated active support in agencies for persons with developmental disabilities to increase staff assistance and service user engagement. A systematic review identified two studies in which researchers reported three experimental evaluations of active support. Only one experiment showed a clear functional relationship between active support with “ineffective” to “questionable” percentage of nonoverlapping data points effect sizes and acceptable percentage of all nonoverlapping data points effect sizes. Two experiments did not show experimental control; however, there was evidence that the investigators in these studies did not sufficiently manipulate the independent variable. Based on these data, active support only meets Chambless and Hollon's (1998) criterion for a “promising treatment” but not an evidence-based practice. Future research on active support should demonstrate that the experimenter manipulated the independent variable and reported data on individual participants.