In recent years, due to proliferation in the use and transport of petroleum in the marine environment, an extensive literature has developed concerning the effects of accidental spillages. One approach toward assessement of potential effects, of both large scale spillage and low-level discharge, has been to conduct laboratory bioassay studies to determine short-term lethal and sublethal effects on individual marine species. While that approach is severely limited in predicting ecosystem effects, it does serve to bring into focus the complexity inherent in oil-seawater mixtures. The specific objective in this research was to measure aqueous phase concentrations of No. 2 fuel oil and mortality of shrimp when three different methods of oil-seawater contact were used.