Wind tunnel testing of reduced-scale models is a valuable tool for aerodynamic development during the early stages of a new vehicle program, when basic design themes are being evaluated. Both full-and reduced-scale testing have been conducted for many years at the General Motors Aerodynamics Laboratory (GMAL), but with increased emphasis on aerodynamic drag reduction, it was necessary to identify additional facilities to provide increased test capacity. With vehicle development distributed among engineering teams around the world, it was also necessary to identify facilities local to those teams, to support their work. This paper describes a cooperative effort to determine the correlation among five wind tunnels: GMAL, the Glenn L. Martin Wind Tunnel (GLMWT) at the University of Maryland, the Institute of Aeronautics and Space (IAE/ALA) TA-2 Wind Tunnel in Brazil, the Monash University Wind Tunnel in Australia, and the Korea Aerospace Research Institute Low Speed Wind Tunnel (KARI LSWT). Correlation tests were conducted using a vehicle model with interchangeable body modules and additional parts, to determine the relationships of measured aerodynamic force and moment coefficients among the tunnels. Despite the significant differences among facilities, the correlation results were satisfactory for reduced-scale wind tunnel development of future General Motors Co. (GM) vehicles. Correlation equations were defined, allowing conversion of data from one tunnel to equivalent values at another. This paper will present the physical descriptions and airflow characteristics of the wind tunnels, the test equipment and procedures, and the correlation results.