An adjustable screen re don system is presented. The present invention screen retention system comprises a mesh Of perforate screen retained within a frame composed of frame members have channel cross sections. The screen is formed with a rolled or U-shaped edge hem. The edge hem having a free edge that folds inwardly over the inner face of the screen and is parallel to, and spaced above, the inner face of the screen. The framing members are channel section extrusions which contain features for retaining, tensioning and locking the screen. The adjustable screen retention system herein presented improves upon the prior art by providing a more secure attachment of the screen within the channel of the frame members thereby providing increased resistance to screen impact loading. The new system also provides for a broader range of screen of tensioning adjustment than has heretofore been available and further electrically isolates the screen from the walls of the channel.