A Practice Note examining the requirements for jurisdiction over claims against sovereign defendants (including foreign states and their political subdivisions, agencies, and instrumentalities) under the Foreign Sovereign Immunities Act's "commercial activity" exception to sovereign immunity, codified at 28 U.S.C. § 1605(a)(2). This Note analyzes the core jurisdictional requirement that, for this exception to apply, the plaintiff's action must be based on a foreign state's commercial activity or an act in connection with a foreign state's commercial activity.