Despite the importance of clinician-patient communication, little is known about rates and predictors of medication miscommunication. Measuring rates of miscommunication, as well as differences between verbal and visual modes of assessment, can inform efforts to more effectively communicate about medications. We studied 220 diverse patients in an anticoagulation clinic to assess concordance between patient and clinician reports of warfarin regimens. Bilingual research assistants asked patients to (1) verbalize their prescribed weekly warfarin regimen and (2) identify this regimen from a digitized color menu of warfarin pills. We obtained clinician reports of patient regimens from chart review. Patients were categorized as having regimen concordance if there were no patient-clinician discrepancies in total weekly dosage. We then examined whether verbal and visual concordance rates varied with patient's language and health literacy. Fifty percent of patients achieved verbal concordance and 66% achieved visual concordance with clinicians regarding the weekly warfarin regimen (P < .001). Being a Cantonese speaker and having inadequate health literacy were associated with a lower odds of verbal concordance compared with English speakers and subjects with adequate health literacy (AOR 0.44, 0.21-0.93, AOR 0.50, 0.26-0.99, respectively). Neither language nor health literacy was associated with visual discordance. Shifting from verbal to visual modes was associated with greater patient-provider concordance across all patient subgroups, but especially for those with communication barriers.Clinician-patient discordance regarding patients' warfarin regimen was common but occurred less frequently when patients used a visual aid. Visual aids may improve the accuracy of medication assessment, especially for patients with communication barriers.