By using electrical conductivity and static and dynamic light scattering measurements, the behavior of water-oil (w/0) microemulsions formed by Aerosol OT dissolved in toluene has been examined. To study the effect of the droplet volume fraction on the microemulsion behavior, the water and the surfactant concentrations were systematically modified and the temperature dependence was also studied. The scattering intensity and the apparent diffusion coefficients are analyzed with a model involving the Carnahan-Starling hard-sphere model including an attractive term. It was found that attractive interactions become important in w/o microemulsions containing w(o) > 37. No percolation threshold is detected at the droplet volume fraction and temperature values used in this work.