The objective of this project was to develop molecular genetic tools for using mtDNA markers in coho salmon stock identification problems. Three steps were required to apply DNA technology to stock separation:  (1) identification of variable regions for the DNA (markers), (2) development of a method to rapidly obtain data for the markers, and (3) assembly of baseline information about the distribution of the markers in stocks of interest. The PCR oligonucleotide primers developed and assembled amplified most of the mdDNA of coho salmon in fragments with sizes that are easy to work with, they amplify the mtDNA of other Pacific salmon species as well as some of the mtDNA of more distantly related species.  Primers were used to amplify mtDNA fragments from a set of test samples in order to identify restriction sites that were variable and subsequently to increase the scope of the study.  From those data, there was substantial genetic variability both within and among most of the collections, and there was a geographical basis to the genetic variability observed.