The impact of an interactive CD-ROM program on the rate of medication administration errors made by nurses was studied. This randomized, controlled, nonblinded study was conducted at three community hospitals. Study participants included 30 registered nurses who had at least one year of nursing experience in acute care and who worked on medical or medical-surgical units. Nurses were randomized to an intervention group that completed an interactive CD-ROM program on safe medication practices or to a control group. Direct observation was used to determine the baseline (preintervention) and postintervention error rates for both study and control groups. Three categories of errors were defined: deviation from safe administration practices (core 1), preparation and administration errors (core 2), and deviations from prescribed therapy (core 3). An error rate was calculated for each nurse, and the error rates for the study and control groups were based on the average error rate for the nurses in each group. The majority of errors made were core 1 errors. The nurse-level data showed a significant decrease in core 1 error rates between baseline and postintervention periods. Core 2 error rates were higher in the postintervention period, but the increase was not significant. Very few core 3 errors were made by either group during either period. An interactive CD-ROM enabled nurses to apply the information learned to identify errors in medication administration and improved adherence to safe medication administration practices.