This paper reports a study of diffusion phenomena occuring during solvent extraction of ginseng extract from dry ginseng slice. Ginseng slice were prepared and extracted in such manner as to meet the conditions required by the diffusion theory derived from Fick`s law. The diffusion coefficient under these conditions varies with slice thickness, solvent, cell structure, and temperature. Those knowledge of the above factors which may influence the extraction process are useful for intelligent design of an efficient extraction procedure.