Early and adequate risk stratification is essential in patients with suspected acute coronary syndrome (ACS). The aim of the present study was to investigate whether glycogen phosphorylase BB (GPBB) could add prognostic information in the context of contemporary sensitive troponin I determination and B-type natriuretic peptide (BNP). Patients with suspected ACS were consecutively enrolled at 3 German study centers from January 2007 through December 2008. Troponin I, GPBB, and BNP were determined at admission. Follow-up information on the combined end point of death, myocardial infarction, revascularization, and hospitalization owing to a cardiovascular cause was obtained 6 months after enrollment. In total 1,818 patients (66% men) were enrolled of whom 413 (23%) were diagnosed as having acute myocardial infarction and 240 (13%) as having unstable angina pectoris, whereas in 1,165 patients (64%) an ACS could be excluded. Follow-up information was available in 98% of patients; 203 events were registered. GPBB measured on admission predicted an unfavorable outcome with a hazard ratio of 1.24 (p <0.05) in an unadjusted Cox regression model and showed a tendency with a hazard ratio of 1.13 (p = 0.07) in a fully adjusted model. Kaplan–Meier analysis revealed a poorer outcome in patients with increased GPBB levels amendatory to the information provided by troponin I or BNP. In conclusion, GPBB measurement provides predictive information on midterm prognosis in patients with chest pain in addition to BNP and troponin I.