Investigation of molecular weight and some physicochemical properties of ricin D was carried out. Sedimentation constant, s20, was calculated to be 4.64×10−13 in acetate buffer solution (μ=0.1) of pH 5.0. Molecular weight of ricin D was measured by Archibald's method and calculated to be 6.00×104. Electrophoretic mobilities were measured at pH values 3.6, 5.0, 6.0, 8.0, and 9.0 respectively and the isoelectric point of ricin D was found to be pH 5.9. Ultraviolet absorption spectrum of ricin D was consistent with that of a common protein.