[en] Ecological risk assessment estimates the nature and likelihood of effects of human actions on nonhuman organisms, populations, and ecosystems. It is intended to be clearer and more rigorous in its approach to estimation of effects and uncertainties than previously employed methods of ecological assessment. Ecological risk assessment is characterized by a standard paradigm that includes problem formulation, analysis of exposure and effects, risk characterization, and communication with a risk manager. This report provides a framework that applies the paradigm to the specific problem of assessing the ecological risks of petroleum in soil. This type of approach requires that assessments be performed in phases: (1) a scoping assessment to determine whether there is a potential route of exposure for potentially significant ecological receptors; (2) a screening assessment to determine whether exposures could potentially reach toxic levels; and (3) a definitive assessment to estimate the nature, magnitude, and extent of risks. The principal technical issue addressed is the chemically complex nature of petroleum--a complexity that may be dealt with by assessing risks on the basis of properties of the whole material, properties of individual chemicals that are representative of chemical classes, distributions of properties of the constituents of chemical classes, properties of chemicals detected in the soil, and properties of indicator chemicals. The advantages and feasibility of these alternatives are discussed. The report concludes with research recommendations for improving each stage in the assessment process