The effective relative permittivity and electric conductivity of suspensions of 15 nm particles of aluminium oxide (alumina) in base Milli-Q and Milli-Ro water were determined at six different temperatures in the range (298.15 to 348.15) K, and at eight different concentrations up to 7% mass (2% volume). Present results demonstrate the importance of the volume fraction of nanoparticles, temperature and water purity on the effective relative permittivity and electric conductivity of alumina nanoparticles suspensions. Empirical equations for describing the experimental data are given. Trends for changes in permittivity enhancement and in electric conductivity enhancement with temperature and concentration are examined and discussed. It is found that the conductivity enhancement is larger for alumina nanoparticles in the purer Milli-Q water than in the less-pure Milli-Ro water. Classic models for predicting the relative permittivity of binary systems fail when applied to these nanofluids because the latter exhibit positive relative permittivity changes on mixing. The effect of temperature on electric conductivity is discussed in terms of an Arrhenius-like equation. (c) 2013 Elsevier Ltd. All rights reserved.