Broad bean protein was fractionated into four fractions, so-called 2 S, 7 S, 11 S and 15 S components, by sucrose density gradient centrifugation. 11 S component obtained was homogeneous as judged by polyacrylamide gel electrophoresis. 15 S component was found to be a dimeric form of 11 S component. Molecular weights of 11 S and 15 S components were 319,000 and 599,000, respectively. 11 S component consisted of at least four kinds of acidic subunits with molecular weights of 36,000, 49,000 and 51,000 and three kinds of basic subunits with molecular weights of 19,000, 20,500 and 23,000. The acidic subunits and the basic subunits were present in equimolar amounts in 11 S component. The result of sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the absence of reducing reagent suggests that 11 S component contains at least three kinds of intermediary subunits with molecular weights of 48,000, 59,800 and 61,700.