A Practice Note providing an overview of the Department of Labor regulations defining "plan assets" under Title I of the Employee Retirement Income Security Act of 1974 (ERISA) as amended by Section 3(42) of ERISA enacted under the Pension Protection Act of 2006 (PPA). This Note describes when a private investment fund (such as a private equity fund) will be treated as an entity holding "plan assets" for purposes of ERISA, explains several important exceptions to this general rule, and discusses the consequences for an entity that is deemed to hold "plan assets" under the rules (a "look through" or "plan asset" vehicle).