Effectiveness VS Efficacy: Effective treatment provides positive results in a usual or routine care condition that may or may not be controlled for research purposes but may be controlled in the sense of specific activities are undertaken to increase the likelihood of positive results. Effectiveness studies use real-world clinicians and clients, and clients who have multiple diagnoses or needs. In contrast, Efficacious treatment provides positive results in a controlled experimental research trial. A study that shows a treatment approach to be “efficacious” means that the study produced good outcomes, which were identified in advance, in a controlled experimental trial, often in highly constrained conditions. Translating efficacious practices to routine practice settings to produce effective results is one of the more challenging issues of evidence-based practice.