This document contains interim rules governing parity between medical/surgical benefits and mental health benefits in group health plans and health insurance coverage offered by issuers in connection with a group health plan. The rules contained in this document implement changes made to certain provisions of the Internal Revenue Code of 1986 (Code), the Employee Retirement Income Security Act of 1974 (ERISA or Act), and the Public Health Service Act (PHS Act) enacted as part of the Mental Health Parity Act of 1996 (MHPA) and the Taxpayer Relief Act of 1997. Interested persons are invited to submit comments on the interim rules for consideration by the Department of the Treasury, the Department of Labor, and the Department of Health and Human Services (Departments) in developing final rules. The rules contained in this document are being adopted on an interim basis to ensure that sponsors and administrators of group health plans, participants and beneficiaries, States, and issuers of group health insurance coverage have timely guidance concerning compliance with the requirements of MHPA.