Abstract Changes in the pattern of radial growth of young Pinus ponderosa in the Black Hills of South Dakota were as predicted by the Schwendener-Metzger theory of bole development. Before thinning, the annual layers were widest at about 80 to 85 percent of tree height and narrowest at 20 to25 percent of tree height. Radial growth of stagnated stands was increased by thinning; the most rapid growth usually began the third year after thinning and continued 3 to 6 years. During this period, the annual layers were widest at the tree bases and narrowest at about 70 percent of treeheight. This change in growth pattern resulted in greatly increased taper. Average form quotients, bole form, and ratios of height to diameter approached the averages of Black Hills ponderosa pine. After the period of maximum radial growth, the annual layers were widest at about 85 percentof tree height and narrowest at about 25 percent of tree height. Thinning an overstocked but not stagnated stand did not change the pattern of vertical distribution of annual increment, bole form, taper, or ratios of height to diameter.