A Practice Note discussing investigations under Section 232 of the Trade Expansion Act of 1962, which are conducted by the US Department of Commerce's Bureau of Industry and Security (BIS) to determine if certain goods are being imported into the US in quantities or under circumstances that threaten to impair US national security. This Note includes an overview of Section 232 and its use over the years, with a focus on investigations conducted by the Trump administration (including the resulting tariffs on steel and aluminum imports) and the Biden administration.