Hydrolyzed wheat gluten (WG) and wheat starch (WS) showed substantial reinforcement effects in rubber composites. Because of the different abilities of WG and WS to increase the modulus of rubber composites, the composite properties Could be adjusted by the variation of the ratio of WG to WS as a cofiller. WS and WG composites were less temperature-dependent than carbon black (CB) composites, and the cofiller composites became more temperature-dependent as the WG content increased. WS showed the greatest reinforcement effect, whereas WG and CB had similar effects. The cofiller composites had a reinforcement effect between those of the WG and WS single-filler composites. For fatigue and recovery properties, the initial structures of the WS composites were more stable at smaller strains, but they broke down at larger strains without much recovery. The WG and CB composites, on the other hand, had a less stable composite structure at smaller strains but had better recoverability. The cofiller composites reflected the characteristics of the single-filler composites. With respect to the residual structures of these composites after the strain cycles, the WG composites were the most elastic in the small strain region, and the structures of the cofiller composites became less elastic as the WS content increased. The extent of stress softening indicated that the WS composites had significant structural deformation and were less elastic in comparison with the WG and CB composites. The hydrolyzed WG-dominated composites exhibited viscoelastic behavior similar to that of CB composites. (C) 2009 Wiley Periodicals, Inc.(dagger) J Appl Polym Sci 114: 2280-2290, 2009