The polyaniline/iron nanocomposites with both conducting and magnetic properties have been prepared by cryomilling (high-energy ball milling under cryogenic temperature), in which the average size of iron grains attains 20 nm. Enhanced coercivity of 206 Oe and decreased conductivity of 0.1 S cm(-1) at room temperature have been obtained for the nanocomposites containing 10% volume fraction of iron in polyaniline after cryomilling for 20 h. The high value of the coercivity could be considered due to the presence of a fraction of single-domain particles in the nanocomposites. The low value of the conductivity could be considered due to the dedoping of conducting polyaniline with the cryomilling time. (c) 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3157-3164, 2006.