An investigation has been made at high latitudes of regions or patches of isolated electron precipitation with bremsstrahlung X ray images (>4 keV) and simultaneous particle and 391.4-nm data acquired with the Stimulated emission of Energetic Particles payload on the S81-1 satellite. More extensive analyses of the phenomena than were originally reported (Imhof et al., 1985) have now been made. From this investigation it has been found that when some patch regions are processed with greater sensitivity, nearby weaker patches are found. This characteristic suggests that some of them may be parts of larger structures. There is considerable overlap in spectral shape between patches and larger structures, but the energy spectra of the X rays emitted from the patches are, on the average, softer, even at similar invariant latitudes. Although some patches may be associated with auroral substorms as indicated from comparisons with the AE index, the majority are not and therefore appear not be related to westward traveling surges. Most patches are significantly narrower in one direction, consistent with arc-shaped precipitation. Fine structure is present in some patches, and study of the bremsstrahlung X ray measurements indicates that on a statistical basis many of the spikes associated with the fine structure are spatial and not temporal in nature, suggesting multiple arcs. Also consistent with arc structure, the local time variations have been found to display a similarity to those associated with inverted-V events, but the measured electrons are at higher energies than are normally associated with such events. In summary, at least some of the small precipitation patches reported here seem to be parts of larger structures which may encompass a variety of forms, including those that are arc-shaped in nature. ¿ American Geophysical Union 1988