The effect of a static magnetic field, B, on the electrolysis of copper in aqueous solution is investigated using linear sweep voltammetry, impedance spectroscopy, chronoamperometry, rotating disk voltammetry, and analysis of fractal growth patterns. Data are obtained in fields of up to 6 T. There is a large enhancement of the electrodeposition rate (up to 300%) from concentrated CuSO4 solution (c similar to1 M) when pH less than or equal to 1. The effect of the magnetic field is equivalent to that achieved by rotating the electrode. From the pH, viscosity, field direction and concentration dependence of the field effect, the influence of field on the complex impedance, and the equivalence of field and electrode rotation, it is established that the magnetic field influences mass transport by forced convection. Convective flow is modified on a microscopic scale in the boundary layer close to the working electrode. There is no influence on the electrode kinetics. Turbulence sets in for our cell geometry when the product of field and current density exceeds a critical value of about 1000. N/m(3). The competition between gravitational and magnetic forces is dramatically exhibited by the morphology and fractal dimensionality of planar electrodeposits in a flat circular cell. Quantitative comparison is made of the magnitude of various magnetic body forces inducing convection in typical experimental conditions. The results are discussed both in terms of Aogaki's model of a streamline boundary layer, which predicts that the excess limiting current varies as B(1/3)c(4/3), as observed experimentally, and in terms of the electrokinetic effect.