- The Arabian Oryx ( Oryx leucoryx ) is listed as critically endangered by the International Union for the Conservation of Nature and a reintroduction effort currently is underway involving three release sites in the Negev desert of southern Israel. We describe a simulation model developed to project future population trends in view of uncertainties concerning establishment of migration corridors among release sites and post-reintroduction increases in natality rates. We first evaluate ability of the model to simulate observed trends in population growth following reintroductions of Arabian Oryx in Oman, and trends observed to date in the Israeli Negev. We then use the model to project future scenarios in the Israeli Negev under all combinations of three assumptions regarding establishment of migration corridors and two assumptions regarding post-reintroduction increases in natality rates. Model projections suggest (1) no individual site supports a viable population (minimum viable population size has been estimated at 100 individuals) under any of the scenarios; (2) if there are no post-reintroduction increases in natality rates, the area supports a viable metapopulation (101 individuals) only with establishment of migration corridors among all sites; (3) if there are post-reintroduction increases in natality rates, the area supports a viable metapopulation (247 individuals) with establishment of migration corridors among all sites and also with establishment of migration corridors only between Sites A and C (172 individuals). Model projections also suggest that uncertainty regarding natality and migration, which are the rates most critical to management decisions, might be reduced substantially by continued field monitoring of Sites A and C over the next 5 or 6 years; management of Site B (mountainous terrain) remains critical either until increases in natality rates and the establishment of a migration corridor between at least Sites A and C (open, flat terrain) have been confirmed, or until the decision is made to abandon Site B in favor of the establishment of an alternative release site.