In 1951 the Ministry of Civil Aviation made an investigation into the acoustic screening offered by the use of a running-up pen. Tests at London Airport in which a Viking was run up behind an experimental wall constructed of corrugated cement asbestos sheeting fixed to a scaffolding of steel tubing showed that a reduction of some 25 phons could be obtained throughout most of the geometrical shadow of the wall and over a range of distances probably exceeding one mile. Unexpected acoustic characteristics of the experimental wall precluded the collection of the full design data on running-up pens that were sought, but did not detract from the efficacy that was demonstrated. Auxiliary tests suggested that little noise abatement can be achieved by the use of trees or buildings. A prototype running-up pen is now being built at London Airport to find what operational problems are associated with the use of running-up pens and, if possible, the design data still required.