The Sanitary Phytosanitary Code (SPS) is an effort to reduce the technical barriers to trade created by phytosanitary regulations, or trade barriers related to plant and animal health. A key feature of SPS is risk assessment and risk management in determining appropriate quarantine actions which provide an acceptable level of risk to the importer and which can be justified on technical and trade terms. The major problem so far has been in quantifying the effects of phytosanitary regulations in a way that permits objective comparisons. The paper presents a conceptual model for quantifying quarantine related trade barriers. The model provides a basis for combining the two basic components of pest risk analysis, probability of establishment and economic effects, into a management framework and an objective measure. The model framework provides a systematic basis for defining and measuring acceptable risk and for justifying quarantine actions relative to acceptable risk.