Trials have been established in Hawaii to develop spacing guidelines for Eucalyptus saligna plantations. Substantial competition-related mortalicy occurred in densely planted plots of three spacing trials. Data on stand diameter and surviving number of trees on these plots were plotted in logarithmic form to estimate a "self-thinning" or maximum diameter-stand density line. An "operating" maximum line was defined-one representing 70 percent of the total number of trees that could reach any given mean diameter if the stand were allowed to reach the "self-thinning" level. This information provides a guide to the number of E. saligna trees to plant per hectare for selected target diameters at harvest.