In this study, the effects of microchannel height and particle volume fraction of nanofluids on heat transfer and pressure drop characteristics are investigated experimentally. Nano sized TiO2 particles with an average diameter of 25 nm have been dispersed into the deionized water in five different particle volume fractions of 0.25%, 0.5%, 1.0%, 1.5% and 2.0%. The forced convective heat transfer experiments of nanofluids have been conducted in a microchannel, which has four different heights of 200, 300, 400 and 500 gm. A constant heat flux of 80 kW/m(2) has been applied to the bottom wall of the microchannel, and the experiments have been carried out under steady state and laminar flow conditions. The results have been presented with respect to convection heat transfer coefficient and pressure drop. An increase in the microchannel height decreased the heat transfer rate and enhanced the pressure drop. It is concluded that nano sized TiO2 particles in the base fluid have provided higher heat transfer and have not caused an excessive increase in pressure drop with respect to pure water. Convection heat transfer coefficient has also increased with an increase in the volume fraction. (C) 2015 Elsevier Ltd. All rights reserved.