The effect of magnetic field on the potentiostatic current oscillations of iron electrode in 0.5 mol dm(-3) sulfuric acid was studied in situ by digital holography. The orientation of the magnetic field had an obvious effect on the current oscillations: when the magnetic field was vertical to the electrode surface, the magnetic field would cause a cyclotron-like fluid flow of ions and had a negligible effect on mass transport and the oscillations; when the magnetic field was parallel to the electrode surface, the force would drive the charging ions to one side of the electrode and increase the mass transport, resulted in a decrease of oscillation period. The effects were analyzed by holograms and discussed by means of magnetohydrodynamic force. (c) 2005 Elsevier B.V. All rights reserved.