Additive variance for height of loblolly pine (Pinus taeda L.) in Georgia was very low at younger ages (1 to 8) but rapidly increased thereafter. Nonadditive variance increased from ages 1 to 10 and then remained constant through age 26. The ratio of nonadditive variance to total genetic variance increased from 17% at age 1 to a maximum of 82% at age 6, and then declined to 20% at age 26. Heritability values ranged from almost zero to approximately 0.75 with the lowest values occurring at very young ages and for within-family and individual-tree heritabilities. The largest values were associated mainly with family heritabilities and older ages. Almost all estimates of heritability exhibited similar trends; values were very low at early ages and a maximum value between ages 14 and 16. Narrow-sense heritabilities were near zero until approximately age 8, then they increased sharply through age 16 and declined at the final measurement age. Finally, the coeffident of genetic prediction for tree height between juvenile ages (1 to 16) and the final measurement age for tree height, when based on the total genetic component (CGP_G), showed a nearly linear increase from age 1 to age 16. The maximum values for this parameter were those associated with full-sib family means and ranged from 0.13 at age 1 to 0.67 at age 16. The additive (CGP_A) and nonadditive (CGP_D) components of CGP_G followed the same patterns the additive and nonadditive variances followed. FOR. SCI. 39(2):231-251.