Abstract—Genetically modified (GM) soybeans (Glycine max (L.) Merrill) expressing the γ-tocopherol methyltransferase gene (γ-TMT) and the selectable marker phosphinothricin acetyltransferase (PAT) were developed by the Rural Development Administration in Korea. In this study, we used Southern blot analysis to examine the stability of inserted genes in GM soybeans, and enzyme-linked immunosorbent assay (ELISA) was conducted to analyze inherent PAT protein levels. PAT expression levels varied among different plant generations and plant organs isolated from GM soybean. PAT expression was the highest in the leaves of plants at the beginning of the pod stage (R3) (12.36 μg/g) and the lowest in pods collected from plants that were at the fully mature stage (R8) (1.43 μg/g). The PAT protein showed a decreasing pattern of expression during plant growth. As expected, the expression of PAT proteins was not detected in control soybean plants.