A proposal for the Dutch Red List of threatened lichen species was prepared on the basis of the internationally accepted IUCN criteria. According to these criteria species are assigned to six categories on the basis of a combination of rareness and decline. These categories are: presently not threatened, susceptible, vulnerable, endangered, critical, extinct. Species in the last five of these categories are in the Red List. In The Netherlands 695 lichen species have been found. Of these, 326 species (47% of the Dutch lichen flora) are on the Red List. The numbers of species in the various categories are: Susceptible: 84 (12%); Vulnerable: 66 (9%); Endangered: 52 (7%); Critical: 41 (6%); Extinct: 83 (12%). Thirty-three (5%) species extinct before 1900 are excluded from the Red List. Threats and conservation measures are treated for 22 habitats that are important for lichens. Fourty-eight representative species are treated in detail. A rough comparison with the situation in adjacent countries shows the international importance of the Dutch lichen flora.