This document is about a Department of Labor advisory opinion on the application of the ERISA prohibited transaction exemption in section 4975(d)(13) of the Internal Revenue Code to an employee stock ownership plan's (ESOP) purchase of company stock. The Department concludes that the definition of "qualifying employer security" in ERISA section 407(d)(5) applies for purposes of the prohibited transaction exemption, provided the conditions of ERISA section 408(e) are met.