The development of compression systems for advanced twin-spool turbofan engines became increasingly more difficult as stability, performance, weight, and cost reduction goals were increased. Experience indicated that single-spool compressor component tests did not completely duplicate stability limits determined by flight engine tests. A requirement existed for a component test technique to develop the entire twin-spool compression system in a simulated engine environment, with sufficient operating flexibility to reproduce critical operating points that might be incurred during actual engine operation. The Pratt & Whitney Aircraft dual-spool compressor facility was designed and built to meet this requirement. The dual-spool facility has been employed in the development of several advanced models of the JT9D engine, in the JT10D demonstration engine development program, and in a U.S. Air Force sponsored program (F33615-70-C-1549, sponsored by AFAPL), which employed the TF30 compression system to investigate the nature of dual-spool interactions. Comparison of the JT9D dual-spool test data with engine flight test experience has demonstrated a high degree of correlation. The Air Force program showed that compression system instabilities can be induced in either component and can have a variety of dynamic characteristics, depending upon the operating condition prior to the instability.This paper describes such a facility as it was conceived and built at Pratt & Whitney Aircraft and also summarizes a few of the more important programs to which the facility has been applied.