Needle-like particles (maximum length, similar to 2 mu m) of nickel basic sulfate (Ni(OH)(1.4)(SO4)(0.3)) were prepared by forced hydrolysis at 100 degrees C for 2 days of aqueous solutions containing nickel(II) nitrate, nickel(II) sulfate, and sodium acetate in the appropriated concentrations. The needles were characterized in terms of their composition, crystal structure, and electrokinetic behavior. Their structural and compositional evolutions with temperature were also studied. It was found that a dehydroxylation process took place on heating at 500 degrees C after which the particles consisted of a mixture of crystalline NiO and an amorphous nickel sulfate. This compound decomposed at a higher temperature (800 degrees C) yielding NiO. The particles lost the needle-like shape after calcination at 500 degrees C.