A comprehensive study to evaluate the fate and environmental effects of two shoreline cleaners was conducted in the mesocosm beaches at the Shoreline Environmental Research Facility, in Corpus Christi, TX. Experimental treatments included oil only control, oil plus Corexit 9550®, and oil plus CytoSol®. Both in-situ and ex-situ bioassays were performed to evaluate the biological effects to the immediate treatment areas and the adjacent water columns. In-situ test organisms included fiddler crabs (Uca sp.) and oysters (Crassostrea virginica), which were exposed to the immediate treatment areas and the sub-tidal water columns respectively. Sheepshead minnows (Cyprinodon variegatus) were exposed to tank effluent samples according to EPA guidelines. Insufficient TPH concentrations caused acute harm to both the oysters and minnows. The fiddler crab, amphipod, and sediment elutriate assays indicated that the initial oil application was responsible for significant ecological harm. Enhanced recovery due to the shoreline cleaners was suggested by the sediment elutriate test. However, the amphipod test indicated toxicity remained unchanged overtime with the shoreline cleaner applications. Sediment dwelling organisms were at greater risk to oil spills and chemical response agents than their water column dwelling counter parts. This was due both to the higher contaminant concentration and longer contaminant residence times in the beach substrates. This is an abstract of a paper presented at the 23rd Arctic and Marine Oil Spill Program, AMOP Technical Seminar (Vancouver, British Columbia, Canada 6/14-16/2000).