Latex flow is a primary factor which determines the physiological limit of rubber yield. It has been suggested that the stability of lutoids is a major factor controlling flow. A strong positive correlation exists between plugging index (a measure of the magnitude of latex vessel plugging) and brusting index (a measure of lutoid instability). Although these indices are clonal characters strongly correlated with yield, they have limitations when used as breeding parameters in that it is not known whether the physiological phenomena expressed by these indices are heritable in a simple manner. Hence, attempts were made to identify stable biochemical markers related to yield. We were able to identify two characters related to lutoid membrane composition which showed a high correlation with brusting index and plugging index and thereby yield. Lutoids were isolated from latex samples of high and low yielding clones of Hevea brasiliensis. The phospholipid content of the bottom fraction and protein content of the lutoid membrane were estimated in eight clones with four replicates per clone. The results showed a strong negative correlation of these two parameters with brusting index and plugging index. The possibility of using these parameters for screening clones for yield is discussed.