The Cayman Islands is a major offshore financial center and the registered home of thousands of corporations and financial entities. Financial activity in the Cayman Islands is measured in the trillions of dollars annually. One Cayman building--Ugland House--has been the subject of public attention as the listed address of thousands of companies. To help Congress better understand the nature of U.S. persons' business activities in the Cayman Islands, GAO was asked to study (1) the nature and extent of U.S. persons' involvement with Ugland House registered entities and the nature of such business; (2) the reasons why U.S. persons conduct business in the Cayman Islands; (3) information available to the U.S. government regarding U.S. persons' Cayman activities; and (4) the U.S. government's compliance and enforcement efforts. GAO interviewed U.S. and Cayman government officials and representatives of the law firm housed in Ugland House, and reviewed relevant documents.