In this study the Turbulent flow forced convective heat transfer of ?-Al 2 O 3 /water and CuO/water nanofluids inside a circular tube have been investigated experimentally. This study aims to investigate the effects of the volume fraction of suspended nanoparticles and the Reynolds number on the heat transfer coefficient and pressure drop of the sample nanofluids. Results indicate that addition of small amounts of ?-Al 2 O 3 nanoparticles to the base fluid shows a discernible effect on heat transfer coefficients. Increasing the concentration of nanoparticles does not show much effect on heat transfer enhancement. With increasing CuO nanoparticles concentration as well as Reynolds number, convective heat transfer coefficient does not pursue a clear trend. The pressure drop of the dilute nanofluids increased about 20% compared with pure water. Further more heat transfer enhancement is more pronounced for ?-Al 2 O 3 /water nanofluid and the ratio of heat transfer coefficient of nanofluids to that of pure water decreases with increasing Reynolds number. Also, results compared with existing convective heat transfer correlations for nanofluids and possible mechanisms for heat transfer enhancement in turbulent regime are mentioned.