The rheological behaviour of self-vulcanizable rubber blends based on chlorosulphonated polyethylene (hypalon) and carboxylated nitrile ruber (XNBR) has been investigated in terms of effect of blend ratio, carboxyl content of carboxylated nitrile rubber, carbon black filler loading, rate of shear and temperature on viscosity, die swell and power law constants (n and K). The blend system follows the power law model in the experimental range of rate of shear and shows pseudoplastic flow behaviour. XNBR shows higher viscosity than hypalon and in blends an increasing proportion of XNBR increases the blend viscosity at a constant shear stress or rate of shear. XNBR shows maximum die swell and hypalon shows the least. Blends show lower die swell as compared to the single rubbers. Addition of filler reduces die swell and surface roughness of the extrudates.