Wildlife and fisheries markets are end-points in the supply chain of both legitimate and illegitimate or unregulated trade in species and natural products. Molecular ecology provides powerful tools for surveillance and estimation of this trade. Here, I review the application of these tools to market surveys and species in trade, including species identification and molecular taxonomy, population assignment and ‘mixed-stock’ analysis, genetic tracking and capture–recapture by individual identification. I consider the analogy of markets to natural populations and also the unique features that require novel analytical approaches and sampling design. In the most developed of these applications, the molecular ecology of market surveys and confiscated trade shipments has provided independent estimates of illegal, unregulated or unreported exploitation for sharks, elephants and whales. Although each study has taken advantage of information from trade records or official government reports concerning the ostensible levels of exploitation, it is telling that the truer measure of exploitation seems to arise from the market end-point of the supply chain.