The results of an experimental investigation into the use of screens and perforated plates to control the velocity profile emerging from wide-angle diffusers are reported. Tests were undertaken using two screens in diffusers of area ratio 10 and included angles of 45-degrees and 60-degrees. Without the use of screens to control the flow, highly non-uniform velocity profiles occur. Depending upon the porosity of the screens and their location within the diffuser, three principal types of exit velocity profile were found. These included (i) a regime characterized by high-velocity wall layers together with a depleted core region; and (ii) a regime involving a high-velocity region occupying a cruciform flow pattern, together with low-velocity corner regions. However, the most important finding of the work was that, with appropriate choice of porosity and location of the two screens, mean velocity profiles could be achieved which avoided flow separation and displayed a high degree of flow uniformity. These results extend significantly the range of area ratios in which two screens are sufficient to ensure uniformity of the velocity profile at the exit plane of wide-angle diffusers.