Threatened species lists are widely consulted as sources of information on the conservation status of species. However, their application to planning for conservation is limited because they have not been developed systematically, and because the criteria used to judge extinction risk are subjective. Recently, new proposals have been made to increase the broader usefulness of these lists, and some elements of these proposals are reviewed here. Apart from indicating the geographical and taxonomic groups containing most threatened species, these lists can provide other kinds of information. Some data from threatened species classifications using quantitative criteria provide a new method for estimating extinction rates in a variety of vertebrate taxa. This analysis suggests that over the next 100 years, the extinction rate could be as higs as 15-20% in these groups. These values are comparable to those based upon extrapolations from species-area curves. However, allocating threatened species categories is only a first step towards developing rational systems for setting conservation priorities. These systems will need to consider a quite different set of variables, including those for incorporating species conservation priorities in area-based planning.