The growth of Hevea brasiliensis, reflected by the primary biomass formation, competes directly with latex production which corresponds to secondary biomass synthesis. Five clones with very different growth and yield characteriatics were studied as follows : AF 261, AVROS 2037, PB 217, GT1 and PB 235. Several groups of each clone were compared, namely unopened trees, exploited but unstimulated trees and finally exploited trees with the same tapping intensity but with increasing Ethrel stimulation. The results show that the respective primarry and secondary biomass products lead to a linear regression which reflects the competition between the two synthetic functions ; the repartition coefficient between these functions is dependent on the clone and its physiological characteristics. Beyond a cerrtain stimulation intensity, if growth continues to decrease then latex yield also decreases due to disfnctioning of the laticigenous function. The critical level of stimulation is clone dependant. For these five clones, the latex sucrose content and latex Pi content of each group of trees were studied. It appears that the capability of the tree to react with efficiency to stimulation intensity is tightly linked with available sugar in the laticifers ; the latex sugar content is a clonal characteristic in relation to laticifer matabolic activity. Latex i content effectively reflects the matabolic activity level related to yield. Results are discussed in terms of clonal typology, exploitation level and improvement strategy.