Planar magnetic structures are regions of solar wind plasma where the magnetic field orientation is constrained within a fixed plane for durations of several hours. Within these structures, magnetic field discontinuities are seen, with the discontinuity surfaces being almost co-planar. The results of a survey of planar magnetic structures detected by the Ulysses spacecraft are presented. When searching for these events using minimum variance analysis, a large population was detected of magnetic field structures whose directions described small circles in the spacecraft's field of view (as opposed to great circles described by classic planar magnetic structures). It is likely that these small-circle events represents Alfv¿nic structures. Variations in the nature of the structures at various heliographic latitudes and differing solar wind conditions are described. Implications of the results of the survey are discussed. ¿ 1999 American Geophysical Union