Observations in a 30-year-old loblolly pine (Pinus taeda L.) spacing study indicate that closer planting densities support greater basal areas and volumes per unit area early in the life of a plantation, but lose that advantage to wider spacings over time. In comparisons between observed stand behavior at four spacings and that predicted by four growth and yield models, only one of the models predicted the observed behavior. Workers who wish to project growth of loblolly pine plantations should be aware of this stand behavior and include this criterion in evaluating candidate models.