A new Timor Sea Arrangement is to be adopted by Australia and East Timor upon East Timor's full independence. It is a potentially significant achievement in the prospects for joint development of the petroleum resources in the Timor Gap. This article analyses the legal implications of this latest development in the Timor Gap saga. The new Arrangement implements a modified version of the joint development principle enshrined by the earlier 1989 Timor Gap Treaty much more favourably to the imminent East Timor state. However, the uncertain legal status of the new Arrangement raises questions as to its continuing viability following East Timor's independence. Analysis of this Arrangemcnt suggests that it is sufficiently robust to stand the test of time. More generally, it can now be argued that joint development is mandated under international law as a viable legal alternative to straightforward continental shelf boundary delimitation in the presence of common hydrocarbon deposits.