Apparent shear and dynamic complex viscosity measurements at 200 degrees C and 230 degrees C, for a series of blends of a homopolypropylene (PPVC) with maleic anhydride polypropylene (PP-g-MA) and blends of an ethylene-propylene copolymer (PPSC) with PP-g-MA, are reported. The data were taken using a capillary rheometer and a dynamic mechanical thermal analyzer. The results are analyzed in terms of the Cox-Merz rule, Data taken at 230 degrees C for both matrices (viz. PPVC and PPSC) follow the Cox-Merz rule. However, deviations are noted in the blends, especially in compositions wherein PP-g-MA content is above 10 wt%. Cross phase separation and charges in the dispersed phase size (of PP-g-MB) in the two types of measure ment appear to be the cause of the failure of the Cox-Merz rule.