The nanoscale structures of nickel hydroxide and oxide materials attract considerable interest because of their potential application in several fields. This study introduces a facile method to synthesize Ni(OH)(2) nanowalls directly on a Ni foil by chemical treatment with an NH4OH solution. The dimensions and shape of the Ni(OH)(2) nanowalls can be easily controlled by changing the temperature (50-90 degrees C), volume of the NH4OH solution (25-50 ml), and treatment time (24-144 h). After annealing for 1 hat temperatures below 600 degrees C, the as-synthesized Ni(OH)(2) nanowalls transformed into the corresponding NiO nanostructures, without changes in morphology. The formation of the nanowalls and the influence of the temperature on the morphology of the formed nanostructures were analyzed in terms of the growth mechanism.