Nonadherence to medication is a salient cause of poor outcomes of health care and a primary driver of growing health care costs. Little is known about physician communication with patients regarding their adherence to cardioprotective medication. To identify patients' and physicians' beliefs and practices regarding discussions of adherence to cardioprotective medication. Paired patient and physician questionnaires were developed based on the 8-item Morisky Medication Adherence Scale and administered to 2 academic and 2 community-based cardiology practices in the Chicago, Illinois, metropolitan and suburban areas from June 2 to July 22, 2015. Twenty-one cardiologists and 66 of their outpatients 18 years and older participated. Patient and physician beliefs about discussions of adherence to medication, the frequency of such discussions, and physician recognition of patients who are nonadherent to medication. A total of 21 physicians (5 [24%] women) and 66 patients (23 [35%] women; mean age, 71.6 years) participated in the study. Forty (61%) patients reported rarely or never discussing their adherence to medication with their physicians. Of these patients, 8 (13%) had poor adherence and 36 (55%) had moderate adherence. Only 1 of the physicians of the patients with the poorest adherence correctly identified a patient as being poorly adherent. Fourteen physicians (67%) disagreed with the statement, "I am aware of how often my patient misses a dose of medication." By contrast, all of the physicians agreed that it is important for them to discuss adherence to medication with their patients. Physicians acknowledge the importance of discussing adherence to medication with their patients, yet for many reasons these discussions are uncommon. More important, our study found a notable failure by cardiologists to correctly recognize which of their patients were nonadherent. The novel design of our research identified an important yet neglected aspect of clinical practice. We recommend that physicians include a highly specific question about adherence to medication at every patient visit.