OBJECTIVE: Although medical intensive care unit nurses at our institution routinely use the Intensive Care Delirium Screening Checklist (ICDSC) to identify delirium, physicians rely on traditional diagnostic methods. We sought to measure the effect of physicians' use of the ICDSC on their ability to detect delirium. DESIGN: Before-after study. SETTING: Medical intensive care unit of an academic medical center. PATIENTS AND PARTICIPANTS: A total of 25 physicians with >or=1 month of clinical experience in the medical intensive care unit conducted 300 delirium assessments in 100 medical intensive care unit patients. MEASUREMENTS AND MAIN RESULTS: Physicians sequentially evaluated two patients for delirium using whatever diagnostic method preferred. Following standardized education regarding ICDSC use, each physician evaluated two different patients for delirium using the ICDSC. Each physician assessment was preceded by consecutive, but independent, evaluations for delirium by the patient's nurse and then a validated judge using the ICDSC. Before (PRE) physician ICDSC use, the validated judge identified delirium in five patients; the physicians and nurses identified delirium in zero and four of these patients, respectively. The physicians incorrectly identified delirium in four additional patients. After (POST) physician ICDSC use, the validated judge identified delirium in 11 patients; the physicians and nurses identified delirium in eight and ten of these patients, respectively. The physicians incorrectly identified delirium in one patient. After physician ICDSC use, agreement improved between both the physicians and validated judge (PRE kappa = -0.14 [95% confidence interval {CI} = -0.27 to -0.02] to POST kappa = 0.67 [95% CI = 0.38 to 0.96]) and physicians and nurses (PRE kappa = -0.15 [95% CI = -0.29 to -0.02] to POST kappa = 0.58 [95% CI = 0.25 to 0.91]). Nurses vs. validated judge agreement was strong in both periods (PRE kappa = 0.65 [95% CI = 0.29 to 1.00] and POST kappa = 0.92 [95% CI = 0.76 to 1.00]). CONCLUSIONS: Use of the ICDSC, along with education supporting its use, improves the ability of physicians to detect delirium in the medical intensive care unit.