Ferrous dodecyl sulfate, Fe(DS)(2), micellar solution was used to make nanosized magnetic particles whose size is controlled by the surfactant concentration and by temperature. The average particle size varies from 3.7 to 11.6 nm, with a standard deviation ranging from 0.22 to 0.34. In contrast to what is obtained in homogeneous solution, iron ferrite particles can be obtained when the synthesis is performed at very low reactant concentrations and room temperature. Furthermore, nanoparticles are obtained when the syntheses are performed using Fe(II) as reactant whereas in homogeneous solution particles in the micrometric range are formed. The particle crystallinity varies with the synthesis temperature, going from fairly low values at 25 degrees C to fairly high values at 50 degrees C and above. The particles are characterized by superparamagnetic behavior. The saturation magnetization decreases with particle size, which is explained in terms of non-collinear structure at the interface. Particles with low crystallinity are characterized by magnetic diameters smaller than those determined by transmission electron microscopy. This is attributed to crystalline anisotropy.