The concept of the Ducted Propulsor as a quiet propulsive device is relatively new and, because of this, there is a justifiable demand to see evidence that the claims made can be met.Over the last two years, Dowty Rotol have done a considerable amount of test work and have amassed measured data on thrust, noise, efficiency, cowl drag and windmilling drag. The main part of the paper is devoted to presenting these data in order to answer affirmatively and convincingly the aircraft designers' question-will it work?To preface this, the paper reiterates the case for the Ducted Propulsor, the idea of which was introduced some time ago. Briefly, it meets the noise regulations predicted to 1980 and beyond, it is lighter than the equivalent Quiet Propeller and costs less. The performance characteristics are about the same but the propulsor affords the aircraft designer more flexibility. Furthermore, it helps to reduce exhaust pollution.Finally, the paper outlines the current program of work to build and test a fully integrated ducted propulsor power plant.