Novel effects of combining the magnetic and internal electric fields on protein crystallization were studied in this report. Homogeneity in crystal size and ratio of magnetically orientated crystals were significantly increased, when a homogeneous magnetic field of 10T and an internal electric field (a direct current of 2 muA) were applied to the crystallization of hen egg-white lysozyme at the same time. When the directions of the magnetic field and the electric current were parallel, there were not significant effects observed. This result suggests that the Lorenz force is responsible for the coupling effects of the magnetic and internal electric fields. (C) 2003 Elsevier B.V. All rights reserved.