AbstractThis chapter describes the basic properties of genetic markers and introduces some of their uses in forestry. The genetic markers covered include: (1) morphological markers; (2) biochemical markers (monoterpenes, alloenzymes and other protein markers); and (3) molecular markers based on DNA-DNA hybridization, restriction fragment length polymorphism, polymerase chain reaction, random amplified polymorphic DNA, amplified fragment length polymorphism, simple sequence repeats, and expressed sequence tagged polymorphism.