The effects of a high gradient magnetic field on the Ag+/Cu liquid-solid redox reaction were studied. A copper wire was placed on a sheet of chromatography paper wet with silver nitrate aqueous solution. At zero field silver dendrites grew uniformly around the wire. In the presence of a gradient magnetic field (ca. 380 T(2)m(-1)), the dendritic pattern changed drastically. The yield of silver metal increased by about 45%. These results are attributable to the convection of aqueous solution on the surface of the paper which is induced by the magnetic force on the paramagnetic copper ions generated in the reaction.