In order to identify effective features of clinical decision support systems, this study reports on the findings of a systematic review of randomized controlled trials. Investigators identified 70 studies and reported that decision support systems improved clinical practice in nearly 70%. Independent predictors of this outcome included automatic provision of decision support as part of clinical workflow, provision of recommendations rather than just assessments, provision of decision support at the time and location of decision making, and computer-based decision support. Authors conclude that these features should serve as guidelines to improve patient care and minimize the efforts of clinicians in engaging system recommendations.