The effect on an electron beam of the leakage field due to the magnetic domains in an unmagnetized crystal of hexagonal cobalt has been investigated. A conventional electron-diffraction camera was used, the primary beam being limited by a small movable aperture and the deflexions observed on a photographic plate. Both the hexagonal and prism faces were examined. Magnetic effects were found (a) on the primary beam, (b) on the diffraction pattern, (c) on the shadow edge of the diffraction pattern, and (d) on the shadow photograph of the crystal produced by diffuse scattering from the edge of the aperture. These effects are analyzed in terms of the fields produced by the magnetic domains; measurements are made of the size of the domains and of the magnitude of the leakage field at the surface and its variation with the distance from the surface.