Preventing overuse of potentially dangerous medications has continued to be a challenge for the safety movement, despite increasing use of technological solutions such as computerized order entry and clinical decision support. This study targeted prescribing for drugs classified as requiring a black box warning by implementing reminders within an ambulatory electronic medical record. Certain specific alerts, such as warning against prescribing drugs contraindicated in pregnancy or those with high potential for drug–drug interactions, were effective. However, overall prescribing of contraindicated medications did not decrease. Prior studies have also found limited benefit from prescribing reminders in ambulatory care, and a recent systematic review found that point-of-care clinician reminders, such as those used in this study, generally achieved only limited successes.