We examine the stability of magnetic remanences in grains of magnetite near the critical single-domain grain size (do). The magnetic structure of a grain is followed during a 180¿ magnetization reversal, and it is shown that noncoherent reversals can occur even in grains smaller than do. The energy barrier to noncoherent revesal is much lower than that of coherent rotation, so that pseudo-single-domain grain behavior will be exhibited by grains significantly smaller than do. ¿ American Geophysical Union 1994