Immunolocalization of alkaloids in lupin seeds (Lupinus spp.) has been performed by cryofixation and conventional methods. Alkaloids were localized in the protein bodies of the cotyledon cells. Some immunogold particles in the walls of these cells were also observed. There were no differences in the sites of localization between the two mentioned methods. X-ray microanalysis of elements showed the presence of P, Mg, S, and K in the protein bodies of cotyledon cells in lupin seeds. The role of K+ in alkaloids transport is discussed.