A trisonic wind tunnel has been modified to improve its flow quality when operating at transonic speeds through perforated walls and side suctions. The usefulness of such a perforated wall, already known, is reduction of the blockage effect as well as the shock elimination. Two types of perforated walls have been used in this investigation. The first wall had a porosity of about 22% and the holes were drilled perpendicular to the surface. However, the second wall had a variable porosity, 0 to 6%, and the holes were drilled at an angle of 60 degrees with respect to the normal vector of the plate. The flow in the test section of the wind tunnel was surveyed extensively at various Mach numbers ranging from 0.6 up to 1.2. Effect of porosity has been studied by comparing results related to the present perforated with the previous closed wall data for various conditions as. Te amount of suction could be adjusted through the side walls. Flow quality along the nozzle and test section has been studied by a long tube installed in the center of the wind tunnel test section.