The propagation of dense nonaqueous phase liquids (DNAPLs) in water-saturated, homogeneous porous media was investigated. The static distribution of DNAPL after gravity-driven displacement was studied using a number of three-dimensional spill experiments. Fingering intrinsic to the displacement systems was observed in all experiments. The effects of physical and chemical parameters on flow instability were examined for a range of sand grain sizes (fine, medium, and very coarse) and for different DNAPLs (trichloroethylene, trichloroethane, and dibutyl phthalate). Gravitational, viscous, and capillary forces were observed to have a varied influence on the flow behavior in these experiments. Our observations show that the development of finger patterns is sensitive to the porous media grain size, properties of the DNAPL, and spill conditions. By controlling experimental parameters, results are reproducible and yield insight into finger formation and preferential DNAPL flow in homogeneous aquifer materials. This paper discusses the experimental results qualitatively; a companion paper discusses their quantification with fractal concepts. ¿ American Geophysical Union 1995