A method is described for isolating conarachin II in a homogeneous form by the techniques of DEAE‐cellulose chromatography, polyacrylamide gel electrophoresis and sedimentation velocity. The protein contains 0.72% carbohydrate and no phosphate. Hydrogen ion titration curve indicated that the sidechain carboxyl, imidazole and ‐amino groups titrated with normal pKIntvalues and their number agreed with the analytical values obtained from amino acid analysis. However, tyrosine phenolic groups had abnormal pKIntof 1