In the United States, a gasoline fuel blend with alcohol volume fractions of 85% or more is considered (among other fuels) an alternative fuel. As the popularity and usage of high-alcohol content gasoline fuel blends increase, subsurface contamination from these fuels will be of great environmental concern. An important parameter governing the movement of these contaminants in unsaturated porous media is the liquid viscosity. In this study, five sets of experiments are conducted to determine viscosity variations of (a) blends of 15% gasoline with various alcohol mixtures, and (b) mixtures of high-alcohol content gasoline fuel blends with various volume fractions of water. The three alcohols considered in this study are ethanol, methanol, and isopropanol. The viscosity of each liquid mixture is observed using a modified falling-ball viscometer. (c) 2008 Elsevier B.V. All rights reserved.