Nanofluids are heat transfer liquids which contain small volume fractions of suspended nanoparticles, with sizes smaller than 100 nm, in colloidal solutions. Numerous experiments on the static thermal conductivity of these fluids have revealed a greater-than-expected effective thermal conductivity, and thus there is interest in utilizing nanofluids for heat transfer applications. The nanofluid thermal performance under convective heat transfer conditions is of even greater interest. Therefore, we report here our initial convection experiments with nanofluids. Our experimental test section consists of a single millimeter-size, stainless steel tube subjected to constant wall heat flux. The cooling nanofluids, flowed through the test tube, consist of Al 2O3 nanoparticles and deionized water. Both wall temperature and fluid temperature are measured. Compared with base fluid, the Nu of 20-nm Al2O3-deionized water nanofluids had 8% enhancement for φ = 1 vol% but only 3% for φ = 0.5 vol% at Re = 270. Based on the results, the utility of convective heat sinks containing nanofluids are evaluated for contemporary uses.