This document provides a comprehensive review of information and data relevant to the environmental risk assessment of the protein phosphinothricin-N-acetyl transferase (PAT) produced in genetically engineered (GE) plants by genes isolated from  Streptomyces viridochromogenes (pat gene) or Streptomyces hygroscopicus (bar gene) and presents a summary statement about the environmental safety of this protein. All sources of information reviewed herein were publicly available and include: dossiers presented to regulatory authorities; decision summaries prepared by regulatory authorities; peer-reviewed literature; and product summaries prepared by product developers. Many GE plants contain the  pat gene for use as a selectable marker during development. In those cases, there are one or more additional transgenes contained in the plant and the final product is not necessarily glufosinate tolerant. Although this document will not address these additional genes and phenotypes, their presence should be noted when looking at data on the GE plants that express PAT.