Chemical dispersants are used in oil spill response operations to enhance the dispersion of oil slicks at sea as small oil droplets in the water column.Due to the complexity of chemical and physical interactions between spilled oils, dispersants and the sea, an empirical approach to characterizing the interaction between the dispersant and oil slick may provide a useful or practical approach for including dispersant action in a model. The main objective of this research is to create a set of empirical data on three oils and two dispersants that has the potential for use as an input to the ERO3S model. These data are intended to give an indication of the amount of dispersal of these oils under certain conditions.The US EPA is developing an improved dispersant testing protocol, called the baffled flask test (BFT), which is a refinement of the swirling flask test. Use of this protocol was the basis of the experiments conducted in this study. The variations in the effectiveness of dispersants caused by changes in oil composition, dispersant type, and the environmentally related variables of temperature, oil weathering, and rotational speed of the BFT were studied. The three oils tested were South Louisiana Crude Oil (SLC), an Alaska North Slope Crude (Prudhoe Bay Crude Oil, PBC), and Number 2 fuel oil (2FO). The two dispersants with the highest effectiveness scores under certain test conditions reported earlier were selected for this study. A factorial experimental design was conducted for each of the three oils for four factors: volatilization, dispersant type, temperature and flask speed.