The rapid growth of computerized clinical decision support systems (CDSS) and their impact on patient care seem to share a positive relationship. This literature review examined controlled trials that evaluated the efficacy of CDSS on provider performance and patient outcomes. Using data from 100 studies, investigators report that provider performace improved with CDSS using a number of different outcomes, including diagnostic systems, reminder systems, disease management systems, and prescribing systems. The impact of CDSS compared to care without CDSS on patient outcomes was less clear. Discussion includes a number of detailed tables outlining the various categories of provider performance evaluated. The authors conclude by pointing out the rapid adoption of information technology into health care settings but warn that progress and improvements will continue to rely on adequate evaluation of these systems when incorporated. This study builds on a past review that also evaluated the effectiveness of CDSS on patient outcomes.