Among the 34 nominal lamprey species in the Northern Hemisphere, ten are endangered; nine are vulnerable at least in part of their range, and one is extinct. The major cause is habitat degradation through pollution and stream regulation. Four conservation priorities are recommended: 1. The protection of all lamprey species or populations thereof listed as endangered; 2. where needed, the rehabilitation of the spawning streams of non-parasitic species and the removal or circumvention of any barriers preventing access to the spawning sites; 3. the protection of permanent freshwater resident populations of anadromous species, specifically of Entosphenus tridentatus, Lampetra ayresi, L. fluviatilis, Lethenteron japonicum and Petromyzon marinus: 4. the study of the conservation status of Asian lampreys.