China and Japan’s June 2008 agreement in principle on maritime cooperation in the East China Searaised hopes of a significant breakthrough in the parties’ complex and long-standing disputes in thearea. Subsequent progress towards the realisation of a legally binding, formal treaty on, for example,offshore petroleum joint development has been slow to materialise. In fact, the area under disputeappears to have become more rather than less extensive. This paper examines competing maritime andsovereignty claims in the East China Sea together with progress towards maritime cooperation in thecontext of overlapping jurisdictional claims. The paper identifies some of the key challenges that needto be overcome in realizing a functioning joint resource management regime in the East China Sea.