The main methods to characterize population genetic structure at isozyme loci and their applications in forest  trees  were  reviewed.The population genetic structure can be characterized by two  sets  of measurable parameters: single-locus measures and  multilocus  measures.These two sets of parameters and the  relationship  between  them  are  discussed.   The  contribution  of  multilocus  associations  to  the development of population genetic structure and  its  implication  for genetic conservation and breeding are elucidated.