The state of California has recently implemented the Swirling Flask Test (SFT) as the standard method for evaluating the comparative effectiveness of oil spill cleanup agents on petroleum products transported through state waters. Use of this ＇standard ruler＇ will provide an aid in spill response decision-making. This implementation has involved modifications undertaken to address problems encountered with the existing SFT procedure as specified by the U.S. Environmental Protection Agency (EPA). These modifications involve the actual laboratory procedures, chemical analysis, and data reduction techniques. Primary differences between the California (CAL) and EPA SET techniques include use of a closed test vessel, chemical analysis by gas chromatography (GC) and correction for dispersant contribution when estimating effectiveness. These new procedures have been used to evaluate the relative efficacy of two surfactant-based dispersants, Corexits(R) 9500 and 9527, with Prudhoe Bay crude oil.