INTRODUCTION: Diagnostic ambulatory ECG (AECG) monitoring is widely used for evaluating syncope and collapse, and practice guidelines provide recommendations regarding optimal AECG device selection. However, whether physicians utilize AECGs in accordance with the pertinent guidelines is unclear. This study assessed utilization of AECG monitoring systems for syncope and collapse diagnosis by physicians in the United States. METHODS AND RESULTS: A quantitative survey was undertaken of physicians comprising multiple specialties (Emergency Room, n = 35; Primary care, n = 35; Hospitalists, n = 30; Neurologists, n = 30; non-implanting, n = 34 and implanting-Cardiologists, n = 35). Depending on specialty, respondents reported that neural-reflex and orthostatic causes accounted for 17-23%, cardiac causes for 12-20%, and 'neurological causes' (specifically psychogenic pseudo-syncope/pseudo-seizures and acute cerebrovascular conditions) for 7-12%, of their syncope/collapse cases. The choice of AECG technology varied by specialty. Thus, despite patients having daily symptoms, 25% of respondents chose an AECG technology other than a Holter-type monitor. Conversely, when monitoring for infrequent events (e.g., less than monthly), 12-18% indicated that they would choose a 24-48 hour Holter, 20-34% would choose either a conventional event recorder or a mobile cardiac telemetry system, and only 53-65% would select an insertable cardiac monitor . CONCLUSIONS: In evaluation of syncope/collapse, most U.S. clinicians across specialties use AECG's appropriately, but in a substantial minority there remains discordance between choice of AECG technology and guideline-based recommendations. This article is protected by copyright. All rights reserved.