<qa>  How many chest pain patients are present annually?The correct diagnosis of acute coronary syndrome ACS remains a frequent significant challenge for emergency physicians. Over eight million chest pain patients present annually and despite promising advances in diagnosis, over four percent of ACS patients are mistakenly discharged home. While the history and physical, cardiac risk factor assessment, ECG, and cardiac marker determination are all included in the assessment and risk stratification of patients presenting with possible ACS, this assessment is clearly far from perfect. Improved rapid and accurate means of assessment in this population in the ED are clearly needed.ED patients with chest discomfort will be screened and approached for study enrollment. Consenting patients meeting the study inclusion and exclusion criteria will be enrolled. Point-of-care serial cardiac marker measurements will be performed. Based on a web-based computerized randomization system, half 50 the patients willundergo routine central laboratory testing only. Half 50 of the patients will undergopoint-of-care markers performed in the ED in addition to routine central laboratory testing.In this second group, central laboratory test results will be blinded from the ED physicianuntil the disposition time. BNP will be blinded and not reported to physicians for the first 500 patients Phase I. After the first 500 patients have been enrolled, an interim analysis will be performed to determine the clinical utility of BNP in patient assessment. After physician education of these results, the trial will resume for the remaining 500 patients Phase II. In Phase II, BNP levels will be provided to the physicians using the same time and randomization format.The patients and their medical records will be followed for a period of thirty days and sixmonths after enrollment. 