The rheological behavior of natural rubber (NR) and carboxylated styrene butadiene rubber (XSBR) latices and their blends was investigated, with special reference to the effect of shear rate, temperature, and blend ratio. Arrhenius plots of the blends were drawn and the temperature sensitivity of different blends was determined. All the blends exhibit pseudoplastic behavior, i.e., the viscosity decreases with the increase in shear rate because of the break down of total networks within the system. The viscosity-composition curve showed negative deviation on account of the interfacial slip between the phases. The interfacial slip is occurred with the lack of interaction between the polar XSBR and nonpolar NR phases. For predicting the flow behavior of the blends at a particular temperature and the shear rate, master curves were drawn for the blend systems. The pseudoplasticity index values were determined by Power law analysis. Attempts have been made to correlate the experimental values with theoretical predictions, using Haschin, Heitmiller, and Mashelker-Sood models. (c) 2007 Wiley Periodicals, Inc.