This paper presents the performance cycle analysis of a dual-spool, separate-exhaust turbofan engine, with an Interstage Turbine Burner serving as a secondary combustor. The ITB, which is located at the transition duct between the high- and the low-pressure turbines, is a relatively new concept for increasing specific thrust and lowering pollutant emissions in modern jet engine propulsion. A detailed performance analysis of this engine has been conducted for steady-state engine performance prediction. A code is written and is capable of predicting engine performances (i.e., thrust and thrust specific fuel consumption) at varying flight conditions and throttle settings. Two design-point engines were studied to reveal trends in performance at both full and partial throttle operations. A mission analysis is also presented to assure the advantage of saving fuel by adding ITB. Liew, K. H. and Urip, E. and Yang, S. L. and Mattingly, J. D. and Marek, C. J. Glenn Research Center NASA/TM-2005-213660, E-15150, AIAA Paper 2004-3311 WBS 22-066-10-12 TURBOFANS; TURBINES; SPOOLS; TURBINE ENGINES; THRUST; DUCTED FLOW; EXHAUST EMISSION; JET PROPULSION; PERFORMANCE PREDICTION; RELIABILITY ANALYSIS