Epoxidized natural rubbers (ENR-25 and ENR-45) were prepared using the performic epoxidation method. Two-component (ENR-cassava starch) and three-component (ENR-NR-cassava starch) blends were prepared. ENR-25 and ENR-45 were blended with various quantities of gelatinized cassava starch in the latex state. The pure ENR exhibited lower shear stress and shear viscosity than those of the blends with cassava starch. Furthermore, the shear stress and shear viscosity were increased with an increase in the cassava starch concentration. The chemical interaction between the epoxide groups in the ENR and the hydroxyl groups in the cassava starch molecules might be the reason for the increasing trends of the shear stress and shear viscosity. The blends are classified as compatible blends because of the strong chemical bonding between different phases. SEM micrographs were used to clarify the compatibility. Power law behavior with pluglike flow profiles was observed for all sets of ENR-NR-cassava starch blends. Very low power law index values (<0.34) and highly pseudoplastic fluid behavior were also observed. The log additive rule was applied to plots of zero shear viscosity (consistency index) and the shear viscosity versus the concentration of ENR-25. Positive deviation blending was observed, which indicates compatible blends. (C) 2003 Wiley Periodicals, Inc.