Coral-like nickel structures composed of polycrystalline nanowires with an average diameter of 100 nm were synthesized via a convenient dipolar-interaction-directed self-assembly process. Studies show that the acicular nanocrystallites may magnetize one another by dipolar interaction in an arbitrary direction. leading to the formation of coral-like structures. It is found that the coercivity (H-c) value of the as-prepared sample (ca. 193 Oe) is higher than that of bulk Ni (100 Oe), which is probably related to the coral-like structures of nickel nanocrystallites. (C) 2004 Elsevier B.V. All rights reserved.