Crude oil and/or refined oil products accidentally released into coastal or oceanic waters will result in the formation of surface slicks that create hazards to sea life. Such releases can be mitigated by the use of chemical dispersants under appropriate conditions. Assessing the effect of the application of dispersants requires reliable performance evaluation technologies and measurements so that performance results can be duplicated. Experiments were conducted with four methods to evaluate the performance of dispersant agents in support of EPA's Releases Control Branch, Risk Reduction Engineering Laboratory. The work is an element of the research program that supports the EPA work group concerned with Subpart J (Dispersant Effectiveness and Toxicity) of the National Contingency Plan (NCP). Tests were performed with five types of oil and three types of commercially available dispersants. Statistical analyses of the test results on the effects of experimental variables (test method, oil type, dispersant type, and analytical wavelength in UV-visible spectrophotometric measurements) are presented and discussed.