The flow through a perforated wall was investigated by using a modification of Tollmein's exact solution for an open jet (Durand, W.F., Aerodynamic Theory, vol 3). Derivations were based on the assumption that the flow could be treated similarly to that of a free jet. Experimental verification was obtained by using a small wind tunnel operating at a constant velocity of 21.7 m/sec. Pressure measurements were made for the open-jet arrangement of the tunnel at stations 3, 6, 9, and 12 in. along the wall. Perforated walls were then fitted on the test area, and pressure measurements and velocity profiles were made for the same stations. The velocity profiles were obtained by means of a single total head probe flattened to read a minimum 0.015 in. from the wall. Static pressure readings were made with a probe located at the center line of the tunnel. The experimental results indicated that the flow through perforated walls is a mixing phenomenon and that the Reynolds number influence is negligible.