Magnesium ferrite particles consisting of nanocrystallites were synthesized by sol-gel and coprecipitation methods. Their mean crystalline size increased with increasing calcination temperature. At the same calcination temperature, the sol-gel-derived sample always had bigger mean crystalline size than the coprecipitation-derived sample, implying that the sol-gel method facilitated the formation of magnesium ferrite crystallites. Most of the sol-gel-derived magnesium ferrite particles had a lamellar structure consisting of nanocrystallites, which were probably derived from the porous dried gel precursor. The magnesium ferrite particles had superparamagnetic properties at 27 degrees C, and their saturation magnetization increased with increasing size.