This is a web-based lesson on the principles of rational prescribing. It includes three cases and addresses polypharmacy, adverse drug events, and off-label prescribing. The principles apply to all patient populations, but this lesson focuses on older adults because they constitute a large and growing population at high risk of polypharmacy and unwanted side effects of medications. The lesson utilizes PowerPoint slides, audio, and interactive features including focus questions within the cases and a specially created drug interaction game. Printable resources available for download include two Beers List tables (one by drug type and severity rating and one by disease/condition and severity rating), and a sample medication grid for patient use. The lesson is available free and may be taken for CME credit if desired (registration and a passing a post-test are required). The lesson requires about 30 minutes to complete. It is one of five lessons in the SmartPrescribe curriculum developed by the Wake Forest University School of Medicine to teach prescribers about the need for evidence-based prescribing and the influence that drug company marketing has on medical practice.