Information on the relationship of heartwood development to site quality, competitive index, tree age, and tree size for loblolly (Pinus taeda L.) and longleaf (P. palustris Mill) pine is presented. Twenty-nine loblolly and 26 longleaf pine stands representing a range of age classes (30 to 170 years) and site indices (12 to 37 m) were sampled in the Southeast. At age class 50, a portion of the loblolly pine growing on site index 24 m and better sites contained sufficient heartwood (≥12.7 cm at 6.7 m) for redcockaded woodpecker (Picoides borealis) (RCW) cavity activity. None of the longleaf pine contained sufficient heartwood until age class 60 because the longleaf pines at age 50 were smaller diameter trees than the loblolly pines. The average codominant and dominant loblolly pine contained sufficient heartwood at age class 70 on site index 27 m and better sites and for all sites by age class 80. The average longleaf pine contains sufficient heartwood for RCW cavity activity on all sites at age class 90.