Simulated beaches in the Shoreline Environmental Research Facility wave tanks were used to perform a comparative evaluation of the ecological effects of shorelines impacted by oil and chemically dispersed oil (CDO). Sediment samples were collected from both inter-tidal and sub-tidal regions following test oil applications in the wave tanks. Inter-tidal samples were subjected to two ex-situ bioassays, the first using the marine amphipod Leptocheirus plumulosus according to protocols described by ASTM (1997) and the second using the luminescent bacteria Vibrio fisheri with the Microbics Microtox® system using a procedure described by Meatus et al. In the upper-inter-tidal zone, the amphipod test showed a greater toxic response to exposures of oil impacted sediments compared to CDO impacted sediments. TPH levels in the CDO tanks were equivalent to background levels. Much higher TPH levels were measured in sediments from the oil tanks. The amphipod mortality correlated well with measured TPH values from the samples taken at 24 hr. The Microtox elutriate test indicated a toxic response with sediments collected from tanks contaminated with oil, but not with CDO. Microtox effects correlated well with TPH values from sediment samples collected at 96 hr. The Microtox elutriate test might lack the sensitivity required for optimal evaluation of sediment TPH dose-response. CDO in near-shore environments did not increase the effects observed for sediment-dwelling amphipods. It might also reduce oil exposure to upper-inter-tidal zone environments, decreasing the potential for toxic effects to organisms dwelling in this environment, and increasing the potential rate of recovery for a near shore system following an oil spill. This is an abstract of a paper presented at the 22nd Arctic and Marine Oil Spill Program, AMOP Technical Seminar (Calgary, Alberta, Canada 6/2-4/99).