BACKGROUND: Good patient understanding of basic medication-related information such as directions for use and side effects promotes medication adherence, but information is lacking about how well patients understand basic medication-related information after their office visits. OBJECTIVE: The purpose of this study is to investigate post-visit patient understanding about newly prescribed medications. DESIGN: Secondary mixed methods analysis comparing patient survey responses about newly prescribed medications to information conveyed by physicians during office visits (from audio recordings of office visits). PARTICIPANTS: Eighty-one patients aged 50 and older who discussed newly prescribed medications during an outpatient office visit. MAIN MEASURES: Accurate patient identification of medication dose, number of pills, frequency of use, duration of use, and potential side effects. KEY RESULTS: The 81 patients in this study received 111 newly prescribed medications. For over 70% of all newly prescribed medications, patients correctly identified the number of pills, frequency of use, duration of use, and dose, regardless of whether the physician mentioned the information during the office visit. However, for 34 of 62 medications (55%) for which side effects were not conveyed and 11 of 49 medications (22%) for which physicians discussed side effects, patients reported that the medication lacked side effects. Analysis of transcribed office visits showed that potential reasons for this finding included failure of physicians to mention or to use the term side effects during visits, the prescription of multiple medications during the visit, and lack of patient engagement in the conversation. CONCLUSIONS: Many patients correctly identified information related to directions for taking a newly prescribed medication, even without physician counseling, but when physicians failed to convey potential medication side effects, many assumed that a medication had no side effects. It may be sufficient for physicians to provide written information about medication directions and dosing, and tailor their limited time to discussing medication side effects.