This report considers the question whether the UK should opt in to the negotiation of the proposed Regulation reforming Eurojust. The proposal, which was published in July, seeks to reform Eurojust's governance and management, the nature of its powers and to provide for its accountability. It was brought forward by the Commission alongside the proposal to create a new European Public Prosecutor's Office (EPPO). Both proposals include provisions weaving the two bodies together. Another report inviting the House to issue a Reasoned Opinion challenging the proposed EPPO on the grounds of subsidiarity, has been published alongside the present report. Under the EU Treaties the UK is entitled to opt-in to the negotiation of Justice and Home Affairs legislation such as this proposed Regulation reforming Eurojust.It is acknowledged that the interweaving of the two bodies complicates the question of whether the UK should opt in to the negotiation of the Eurojust Regulation but nonetheless it is recommended that the Government should opt in, given the important work undertaken by Eurojust and, in light of the provisions dealing with the proposed EPPO, the need for the UK to participate in the negotiations in order to improve the Regulation