Assemblies of ferromagnetic cylinders made of Ni with diameters ranging from 35 to 250 nm were produced by electrodeposition in nanoporous membranes. The large coercive fields of Ni nanowires at low temperature could be accounted for by the curling mode of magnetization reversal, taking into account the distributions of win diameters and orientations. The coercive field of the nanowires of the smaller diameter range decreased from 1500 Oe at 20 K to 200 Oe at 300 K nearly linearly. (C) 1996 American Institute of Physics.