Using the Davidse-Maissel diode sputtering system, the distribution of material deposited in the substrate plane during sputtering is studied as a function of power, sputtering pressure, target-to-collector spacing and electrode shielding. Both rf and dc sputtering are investigated. The target is a cobalt disk surrounded by concentric rings of nickel, iron, and copper; the concentration of each component in the deposit (collected on glass slides) is determined through x-ray fluorescence analysis. A mathematical relationship between the local deposition rate on the substrate and the emission from the source is derived. The proposed model describes the observed distribution as arising from the superposition of two sources: (1) a uniform disk, and (2) a ring of infinitesimal width at the perimeter (both sources emitting with a cosine distribution). The latter phenomenon is due to the fact that the dark space of the glow discharge can wrap around the edge of the electrode.