About two long-chain fatty acid ester groups per rubber chain are retained in Hevea rubber, even after treatment of the rubber with proteolytic enzyme and reprecipitation or acetone extraction. The fatty acid esters and phosphorus compounds were perfectly removed by transesterification of rubber solution with sodium methoxide or saponification with KOH. Almost all the proteins were removed by saponification or deproteinisation, while they remained even after transesterification. The gel content of rubber was reduced to almost zero by transesterification or saponification. Huggins k constant of the soluble fraction was reduced apparently by these treatments. The branch-points comprising phospholipid esters in Hevea rubber were presumed to be decomposed to form linear molecules.