Spherical MgCl2·nEtOH was prepared by adducting ethanol to MgCl2 using melt quenching method. Effect of molar ratio of [EtOH]/[MgCl2] = 2.8-3.05 on the morphology and particle size of the MgCl2·nEtOH were studied. The best adduct of spherical morphology was obtained when 2.9 mol ethanol to 1 mol MgCl2 was used. An emulsion of dissolved MgCl2 in ethanol was prepared in a reactor containing silicon oil. Stirrer speed of the emulsion and its transfer rate to quenching section that work at -10 to -40°C are affected by the particle size of the adduct particle. The adducted ethanol was partially removed with controlled heat primary to catalyst preparation (support). Treatment of the support with excess TiCl4 increased its surface area from 13.1 to 184.4 m2/g. Heterogeneous Ziegler-Natta catalyst system of MgCl 2 (spherical)/TiCl4 was prepared using the spherical support. Scanning electron microscopy studies of adduct, support, and catalyst obtained shown spherical particles, however, the polyethylene particles obtained have no regular morphology. The behavior indicates harsh conditions used for catalyst preparation, prepolymerization, and polymerization method used. © 2006 Wiley Periodicals, Inc.