The effect of processing conditions and type of mixers on the mechanical performance of different compositions of natural rubber/polypropylene (NR/PP) blends are investigated. The use of 0.3;dicumyl peroxide in 60;natural rubber blends under optimised processing conditions resulted in the best mechanical performance of the blend. High shearing rate mixers (Buss-Ko kneader) afforded blends with higher initial mechanical performance compared with a laboratory-scale internal mixer (Hampden-RAPRA torque rheometer). The evidence presented indicates the lack of interpolymer formation during the mechanico-chemical process although a small amount of NR undergoes crosslinking during the processing operation. Both melt stability and mechanical properties of NR/PP blends are adversely affected on remoulding: reinjection showed much greater deterioration compared to recompression, albeit high initial mechanical properties of the injection moulded samples.