Shark populations worldwide are declining rapidly from overfishing to supply the international fin trade. These declines have raised serious concerns about potential species and population extinctions and impacts of this large-scale apex predator removal on the health of marine ecosystems. The primary reason for overexploitation of sharks is the absence of effective fishery management for these species by most countries. To address this issue on an international level, the U.N. Food and Agriculture Organization has asked fishing nations to urgently implement management plans for shark conservation. These plans are to emphasize monitoring of shark catches and trade on a species and population-specific basis to allow early detection of overfishing that might otherwise lead to population crashes and extinctions. However, a major obstacle to implementing such monitoring programs is the almost complete lack of information on population genetic structure for most shark species. We therefore propose to develop and use two classes of variable molecular markers (nuclear microsatellites and mitochondrial DNA sequences) to assess the detailed, global-scale population genetic structure of two extremely threatened, CITES Appendix II listed shark species, the basking shark and great white shark, whose fins are highly valued in the market. The molecular marker data will be analyzed using evolutionary (phylogenetic and network) and new Bayesian statistical methods to provide robust estimates of population structure. This study will facilitate, for the first time, the ability to track the population origin of market products from these charismatic and highly threatened species. Furthermore, this research will provide the first assessment of population genetic structure for any globally distributed shark, and serve as a model for future similar studies on other migratory sharks. The threatened status of our study species and previous media interest in our shark research suggest that this study may also generate additional publicity for NSU research.