Raspberry-like magnetic polystyrene microspheres were prepared via soap-free emulsion polymerization using 2,2'-azobis(2-methylpropionamidine) dihydrochloride (V50) as initiator. The effect of polymerization parameters, such as initiator type, initiator content and the feeding sequence on the particle size and morphology of magnetic polystyrene microspheres, were examined. The final magnetic polystyrene microspheres were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA). The experimental results showed that V50 was a suitable initiator for preparation of raspberry-like magnetic polystyrene microspheres. (c) 2007 Elsevier B.V. All rights reserved.