The following systematic review evaluates the effects of computerized physician order entry (CPOE) with clinical decision support (CDS) on the development of an adverse drug event (ADE), as an outcome measure. Ten studies were grouped, based on their settings, into either hospital or ambulatory. CPOE with CDS contributed to a statistically significant decrease in ADEs in 5 studies. 4 studies reported a non-statistically significant reduction in ADE rates, and 1 study demonstrated no change in ADE rates.