The experimental performance of high gradient magnetic separators employing an assembly of ferromagnetic fibers as the collecting agent has been reported by several workers and theoretical treatments for this system have been given. In this paper, we report experimental results for the collection of MnO2and αFe2O3on a single nickel wire in an isolated configuration. The deposit developing on the wire is recorded photographically and by electrical measurement. The deposit develops rapidly on a clean wire and then approaches an asymptotic limit which is many particles thick and depends on the properties of the particles and the flow. The experimental results are given, the procedure is described, and some of the problems are discussed.