The objective of this study was to determine the ability of providers (medical residents and nurse practitioners) on inpatient cardiac units to recognize and appropriately treat patients with clinically significant depression and anxiety among a cohort admitted with acute myocardial infarction. Patients within 72 hours of acute myocardial infarction underwent screening with the Standardized Clinical Instrument for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition module for major depressive disorder (MDD), the Beck Depression Inventory (BDI-II), and the Beck Anxiety Inventory (BAI). In addition, the study psychiatrist and a treatment team clinician independently assessed whether they believed that patients had clinically significant depression or anxiety. Prescription of antidepressants and benzodiazepines during hospitalization was recorded by chart review. Assessments were completed for 74 patients. Providers identified < 15% of patients with current MDD or with a BDI score > or = 10; 11% of patients with current MDD had appropriate treatment with antidepressants. There was no significant correlation of providers' assessment of depression with current MDD, BDI scores, or psychiatrists' clinical assessment of depression. In contrast, providers identified 31% of patients with a BAI score > or = 10 and 50% of patients who were assessed by psychiatrists as anxious; > 80% of patients with high anxiety received benzodiazepines. Providers' assessments of anxiety were significantly correlated with BAI scores and with psychiatrists' clinical assessments. In conclusion, medical residents and nurse practitioners routinely under-recognize and undertreat depression among patients with acute myocardial infarction on inpatient cardiac units. Recognition and treatment of anxiety is substantially better, up to 50% of patients who are found to be anxious by psychiatrists after acute myocardial infarction remain unrecognized.