The paper presents a model for quantifying quarantine-related phytosanitary measures by combining the two basic components of pest risk assessment, probability of establishment and economic effects, into a single management framework, Iso-Risk. The model provides a systematic and objective basis for defining and measuring acceptable risk and for justifying quarantine actions relative to acceptable risk. This can then be used to measure consistency of phytosanitary measures. The Iso-Risk framework is applied using a database of USDA phytosanitary risk assessments. The results show that the USDA risk assessment system produces assessments that are not consistent across a range of intermediate values for consequence or likelihood of occurrence.