Possible environmental effects of marine and hydrokinetic (MHK) energy development are not well understood, and yet regulatory agencies are required to make decisions in spite of substantial uncertainty about environmental impacts and their long-term effects. An understanding of risk associated with likely interactions between MHK installations and aquatic receptors, including animals, habitats, and ecosystems, can help reduce the level of uncertainty and focus regulatory actions and scientific studies on interactions of most concern. As a first step in developing the Pacific Northwest National Laboratory (PNNL) Environmental Risk Evaluation System (ERES), PNNL scientists conducted a preliminary risk screening analysis on three initial MHK cases - a tidal project in Puget Sound using Open Hydro turbines, a wave project off the coast of Oregon using Ocean Power Technologies point attenuator buoys, and a riverine current project in the Mississippi River using Free Flow turbines. Through an iterative process, the screening analysis revealed that top-tier stressors in all three cases were the effects of the dynamic physical presence of the device (e.g., strike), accidents, and effects of the static physical presence of the device (e.g., habitat alteration). Receptor interactions with these stressors at the four highest tiers of risk were dominated by marine mammals (cetaceans and pinnipeds) and birds (diving and non-diving); only the riverine case (Free Flow) included different receptors in the third tier (fish) and the fourth tier (benthic invertebrates). Although this screening analysis provides a preliminary analysis of vulnerability of environmental receptors to stressors associated with MHK installations, probability analysis, especially of risk associated with chemical toxicity and accidents such as oil spills or lost gear, will be necessary to further understand high-priority risks. Subject matter expert review of this process and results is required and is planned for the first quarter of FY11. Once expert review is finalized, the screening analysis phase of ERES will be complete.