Fifteen geographic seed sources of eastern cottonwood (Populus deltoides Bartr.) from the southern United States were used in a provenance-rogeny-lonal test in western Mississippi. Eighty percent of the genetic variation among clones in fifth-ear height resulted from geographic genetic variation. Sixty-our percent of genetic variation in fifth-ear DBH and 21 percent of the variation in stem straightness were likewise associated with geographic differences. No genetic variation was observed among local stands within source in any of these traits. Height, DBH, and straightness all increased from eastern to western origins but only fifth-year height increased from northern origins to southern origins.Narrow-ense hcritabilitics were low, ranging from 0.01 to 0.11 on an individual-ree-within-ource basis. Estimates of non-dditive genetic variance were so small that broad-sense hcritabilitics were only slightly larger than narrow-sense hcritabilities. A cutting production area would give about six to seven percent more genetic gain in fifth-year height and DBH than would give a seedling seed orchard, and about two percent more gain in straight-ness. Genetic correlations between height and DBH were postive and near 10, while the correlations between straightness and those growth traits were low, ranging from 0.01 to 0.31.