DNDO reported that there are currently 444 radiation portal monitors operating at seaports throughout the U.S., which are meeting the requirement to screen all containerized cargo at the 22 seaports with the most container volume. We were unable to determine whether DNDO and CBP initially deployed radiation portal monitors to ensure operational efficiency because the components did not thoroughly document deployment decisions and plans. Although all cargo is being screened, we identified some radiation portal monitors utilized infrequently or not utilized at all.