V/STOL wind tunnel testing performed over the past several years has been guided largely by the well established practices of conventional low speed wind tunnel testing. Since this approach has not always been satisfactory, a recent investigation was made to determine the adequacy of current V/STOL testing methods. The study was particularly relevant to tests of a four-propeller tilt-wing airplane configuration, but the knowledge gained from this study is also applicable to other types of V/STOL airplanes. The principal result of the investigation was finding that some testing practices for conventional models are not adequate for V/STOL models. The key factors that separate conventional and V/STOL testing were found to be the balance interference tares, model power, and angle-of-attack range.