A three year programme aimed at developing new or improved blends of natural rubber with speciality elastomers and funded by The Common Fund for Commodities commenced in July 1992. The programme has four basic themes, each associated with the blending of NR with a particular speciality elastomer, each theme being aimed at a specific applicational area. The progress made in the work is reviewed. Nitrile rubber, NBR, blends with NR are aimed at applications requiring either a degree of damping or a resistance to swelling. It is difficult to devise blends having a satisfactory service performance because of poor phase morphology, low interfacial adhesion and maldistribution of crosslinks between phases resulting from the substantial difference in polarity between the rubbers. Work in this area has concentrated on identifying appropriate cure systems, initially for blends with high acrylonitrile NBR, which overcome this problem. It has been shown that high strength can be obtained in vulcanized gum blends provided there is an even distribution of crosslinks irrespective of a coarse phase morphology. Blends of NR with ethylene-propylene-diene polymer, EPDM, are aimed at producing a combination of good ozone resistance and good strength without employing conventional antidegradants. Good progress has been made in improvement of the overall strength properties of these blends by attention to the mixing procedure and modification of the EPDM during the masterbatch mixing stage and 35;(approx) increases in tensile strength have been observed. Dynamically vulcanized blends of NR with ethylene-propylene rubber, EPR, are prepared by crosslinking the NR during mixing of the blend with the use of a sulphur-based cure system. These blends are aimed at achieving the ozone and weathering resistance of EPR whilst incorporating a substantial proportion of NR. The initial targets have been achieved, namely to identify fast cure systems for the dynamic vulcanization step that do not interfere with the subsequent radical-based vulcanization process whilst also devising procedures that allow dynamic vulcanization and compounding in a single mixing to yield a processable blend. The aim of blending NR with epoxidised natural rubber, ENR, is to obtain very high damping combined with good physical properties and low dependence of dynamic properties on temperature. This is achieved by blending well compounded NR with highly filled and plasticized ENR in which it is essential that the plasticizer is partitioned in favour of the ENR component to ensure comparable viscosities of the two compounds for good blending with comparable moduli for good vulcanizate properties. The preferential location of the plasticizer also ensures suitably low Tg for the ENR phase, and hence the desired low dependence of properties on temperature. The required damping is provided primarily by a very filler loading in the ENR. Statistically designed experiments have provided a basis for selection of the optimum blacktype and loading for each rubber.