The influence of five interstock clones of contrasting vigour on dry matter production and distribution of three Hevea brasiliensis clones grown in the ground nursery over a two-year period was studied. Results obtained after one year of planting indicate that the influence of interstock and scion upon various aspects of growth were generally found to be additive with some showing significant interaction between scion and interstock. The influence of interstock on scion growth was related to the inherent vigour characteristic of the interstock clones. Trees on vigorous interstock (TR 3702 and RRIM 613) produced more dry matter in the above-ground plant parts than those on less vigorous interstocks (H. spruceana and RRIM 600). Leaf area, whole tree dry weight, mean relative growth rate and mean net assimilation rate followed a similar pattern. In these composite trees, it appears that there is competition for photosynthate between scion stem and roots with vigorous interstocks being able to divert more photosynthate to scion stem than roots. The significance of these findings are discussed.