The effect of a magnetic field on the surface topography of (12 0) face Of L-alanine crystals was investigated by an ex situ atomic force microscopy (AFM). The size, density and height of two-dimensional islands observed on the face are markedly different between crystals grown in solutions with and without the homogeneous magnetic field of 5T. The population density of the island increases, and the size decreases, when the magnetic field is applied. The height of the islands also decreases at higher supercooling under 5T. The reason to cause this difference is yet unclear, but the observed difference is in consistence with the observed decrease of growth rate in magnetic field. (C) 2002 Elsevier Science B.V. All rights reserved.