The Morin temperature (T0M) of annealed, monodispersed, nearly spherical particles having diameters (d) between (0.07-0.62) μm have been investigated. A plot of T0M versus 1/d is linear. The extrapolation of this plot between 230 and 262 K to d=∞ gives T0M=264+/-2 K, the Morin temperature of the bulk α-Fe2O3. Furthermore, T0M=0 implies d=83+/-5 A&#778, which is the size limit for the onset of superparamagnetism in this system.