Investigation on non-Newtonian fluid flow in microchannels is of both fundamental interest and practical significance. Flow characteristics of deionized water and the PAM solution over a wide range of Reynolds numbers in fused silica microtubes with diameters from 75 to 250 mu m, fused silica square microchannels with equivalent diameters of 75 and 100 mu m, and stainless steel microtubes with diameters from 120 to 300 mu m, were studied experimentally. The obtained mass flow rate and friction factor for deionized water in smooth fused silica microchannels were in good agreement with theoretical predictions for conventional-sized channels while the deviation for stainless steel microtubes was observed due to the roughness. Friction factors of the PAM solution were much higher than conventional theoretical predictions. Flow behaviors of deionized water and the PAM solution under hydrophobic condition are also studied experimentally. The mass flow rate increased in hydrophobic microchannels compared to untreated microchannels. The drag reduction in hydrophobic channels is greater for rough stainless steel microtubes than for smooth fused silica channels. The effect of surface wettability on the shear thinning PAM solution is also observed to be more evident than on the Newtonian deionized water. (C) 2012 Elsevier B.V. All rights reserved.