Suspension of selected nanoparticles in a base fluid can generate a nanofluid which is one of the most popular fluids in scientific community that has attractive heat transfer characteristics. Its thermophysical properties such as viscosity have important effects on fluid flow and heat transfer characteristics as they affect the pumping power and workability of the fluid. In the present work, the rheological behavior (as shear stress and viscosity with respect to shear rate) of Al2O3-methanol and TiO2-methanol were investigated at different volume fractions and temperatures. The results showed that the fluids appeared as a non-Newtonian fluid with shear thickening or dilatant behavior. The work concluded that shear stress and viscosity increased with volume fractions but decreased with temperatures. The increment was higher in TiO2-methanol compared to Al2O3-methanol nanofluid for both shear stress and viscosity. (C) 2014 Elsevier Ltd. All rights reserved.