Abrin, a highly toxic protein, has been purified and crystallized with a yield of 0.15 per cent from the kernels of Abrus precatorius seeds. The purification involves extraction with 5 per cent acetic acid, ammonium sulfate fractionation and DEAE Sephadex column chromatography. The crystalline abrin is homogeneous with respect to sedimentation criterion. No hemagglutinating activity was detected in crystalline abrin. Based upon sedimentation equilibrium analysis, a molecular weight of 65 × 10 3 was calculated for the protein while amino acid and tryptic peptide map analysis indicates that the crystalline protein contains two peptide chains.