While the National Labor Relations Board (NLRB) was expanding the arbitrator's role in NLRB-related cases, the U.S. Supreme Court was acting to reaffirm, in other types of cases, that the arbitrator's jurisdiction was limited. However, while numerous courts of appeals have approved NLRB deferrals to arbitration, the Supreme Court has done so only indirectly. The standards in the Spielberg Manufacturing case are shown to form the core of the NLRB's deferral policy. The NLRB stated that it would defer to existing arbitration where the subject matter was the same as the unfair labor practice being charged, provided that three conditions were met: (1) that the arbitration proceedings were fair and regular, (2) that all parties had agreed to be bound by the arbitration award, and (3) that the arbitration decision was not repugnant to the purposes and policies of the NLRA. In the board's 1963 Raytheon decision, a fourth standard was added: proof that the issue involved in the unfair labor practice had actually been presented to and considered by an arbitrator. This study also considers new standards developed after the achievement of an NLRB majority by Reagan appointees, and the burden-of-proof issue is addressed. Finally, the General Counsel and NLRB are urged to screen carefully all arbitration cases presented for deferral. A total of 128 references are listed.